The much-anticipated memo, prepared by House Republicans, has finally been made public.

The White House says it "raises serious concerns" about the integrity of justice department and the FBI's Russia investigation while the bureau claims it is inaccurate and omits key facts.

Here's a summary of what we learned:

• The Republican memo alleges the FBI used unsubstantiated evidence to spy on Trump aide Carter Page.

• The memo says the FBI did not tell the authorities their claim to the warrant was based on a dossier funded in part by the rival Hillary Clinton campaign.

• It also claims that information about ex-Trump foreign policy adviser George Papadopoulos, who pleaded guilty in October 2017 to lying to the FBI about his Kremlin-related contacts, triggered the opening of a counterintelligence investigation in July 2016.

Want to know more? For more updates, read our full story here:

Republican memo accuses FBI of abusing power

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Attorney General Jeff Sessions' statement:

"Congress has made inquiries concerning an issue of great importance for the country and concerns have been raised about the Department’s performance. I have great confidence in the men and women of this Department. But no Department is perfect.

"Accordingly, I will forward to appropriate DOJ components all information I receive from Congress regarding this. I am determined that we will fully and fairly ascertain the truth.

"We work for the American people and are accountable to them and those they have elected. We will meet that responsibility."

Worth remembering, Trump pilloried Sessions after he recused himself in March last year from the Russia inquiry once it emerged he had not disclosed 2016 meetings with Moscow's ambassador (Sessions said he forgot).

Sessions' recusal meant he no longer had oversight of the Russia inquiry, including - for example - the power to fire the special prosecutor, Robert Mueller, or bury the results of his investigation.

That inquiry is now in the hands of Deputy Attorney General Rod Rosenstein, whose name crops up in the memo as having approved the controversial surveillance warrant applications.

Today Trump was asked if he might use the memo as an excuse to fire Rosenstein. He told reporters: "You'll figure that one out."

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The White House has said the memo "raises serious concerns" about the integrity of the FBI and justice department's Russia investigation.

"The memorandum raises serious concerns about the integrity of decisions made at the highest levels of the Department of Justice and the FBI to use the Government’s most intrusive surveillance tools against American citizens," White House spokeswoman Sarah Sanders said in a statement.

She added the White House is ready to work with congressional leaders to publicly release a second memo drafted by House Democrats on the same matter.

The House Intelligence Committee blocked the counter-analysis on the same date its members voted to release the Republican-written memo.

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Republican House Speaker Paul Ryan applauded the memo's release, saying he also supported making public a counter memo written by the committee's Democrats.

"Unlike most judicial proceedings, the FISA [Foreign Intelligence Surveillance Act] system depends not on an adversarial process, but instead on the government providing a complete presentation of the facts and circumstances underlying its warrant applications. It is clear from this memo that didn’t happen in this case, and as a consequence, an American's civil liberties may have been violated.

"I am glad that this memo helps to provide greater transparency, and I reiterate my support for the similar release of the minority’s memo once it is properly scrubbed of all intelligence sources and methods."

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Democratic lawmakers are now redoubling demands for their own memo to be released by the House Intelligence Committee, which blocked its release last Monday.

Democrats say their rebuttal lends important context and information left out of the Republican version.

The top Democrat on the House Intelligence Committee, California Representative Adam Schiff, produced their 10-page document.

But it would have to go through the same release process as the Republican one. The committee would need to vote to release the memo, then President Trump would have to declassify it within five days.

Democrats aren’t holding their breath.

However, some congressional Republicans have said they back releasing the Democrats' memo as long as it doesn't divulge intelligence-gathering sources or methods.

Former FBI Director James Comey, who was fired by President Trump in May, tweeted that the memo had "destroyed trust" with the intelligence community.

Anthony Zurcher, BBC News, Washington

The mystery is over, the memo is out, and the results are…pretty much what everyone expected.

Whether the Republican-generated document is as explosive as it had been made out to be depends on how one views the now-infamous Christopher Steele dossier and whether one believes the memo’s assertion that it was an “essential part” of the Carter Page Fisa warrant’s approval - or if there was other pertinent information the Republican memo-writers omitted.

The memo makes the case that the Fisa judge should have been told about information about Steele that could have called his objectivity into question - including his expressed views about Donald Trump, his contacts with the press and the fact that his investigation was funded, in part, by Democratic party interests.

Would such a disclosure have been enough to make the Page warrant request one of only a handful of the tens of thousands of Fisa applications that have been rejected by judges since the system was set up in 1978?

And is the surveillance of Page - who had drawn the attention of US intelligence services as far back as 2013 - enough to call into question the entire Russia investigation, which had been initiated months before the warrant was approved?

Follow Anthony for more updates, external

Tune into World News America tonight at 17:00 Washington time on BBC World.

Last night Katty Kay, external interviewed former White House press secretary Sean Spicer, who described Trump as a "quite forgiving" boss.

Tonight we'll be talking with Republican Congressman Will Hurd, external, who is a member of the House Intelligence Committee that compiled and released this memo.

A reminder that political attacks on the FBI are nothing new.

After the FBI announced in 2016 that it was reopening an investigation into Hillary Clinton's emails - just 11 days before the presidential election - Democrats howled accusations of bias at the bureau.

James Comey, who was later fired by Trump, was accused by Democrats of harbouring anti-Clinton sentiments.

Now it's Republicans who are accusing the FBI of bias.

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Congressman Adam Schiff, the House Intelligence Committee's top Democrat, slammed the memo as a "shameful effort to discredit" the justice department and the FBI.

"The FBI had good reason to be concerned about Carter Page and would have been derelict in its responsibility to protect the country had it not sought a FISA warrant".

He adds that Republicans "would like the country to believe that the investigation began with Christopher Steele and the dossier, and if they can just discredit Mr Steele, they can make the whole investigation go away".

"This ignores the inconvenient fact that the investigation did not begin with, or arise from Christopher Steele or the dossier, and that the investigation would persist on the basis of wholly independent evidence had Christopher Steele never entered the picture."

Ohio Republican Jim Jordan is among the Republican lawmakers tweeting about the memo's release.

Congressman Devin Nunes will be interviewed on Fox News tonight.

As chairman of the House Permanent Select Committee on Intelligence, Nunes commissioned the highly controversial memo.

He will be interviewed at 18:00 Washington time tonight.

George Papadopoulos was a former election adviser to Trump, although you'd be forgiven if you didn't remember his face.

Trump dismissed him as a "low-level volunteer", but he rose to prominence when he became the first person to plead guilty as part of the Mueller investigation.

In late October 2017, court documents emerged showing Papadopoulos had pleaded guilty to lying to the FBI about the timing of meetings with alleged go-betweens for Russia.

He falsely claimed that he had met two figures with Russian connections before joining the Trump campaign in March 2016.

In fact, he met them after joining the campaign. After lying to the FBI, he deleted an incriminating Facebook account and destroyed a phone.

Mother Jones journalist David Corn, who is mentioned in the Republican memo, claims the committee got the date of one of his article's wrong by one day.

By printing the wrong date of the article's release, he says the Republicans have shown their investigation was "sloppy".

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The memo also says the FBI's surveillance warrant application cited as supporting information an article on Yahoo News, which focused on Carter Page's July 2016 trip to Moscow.

"The article does not corroborate the Steele dossier because it is derived from information leaked by Steele himself to Yahoo News.

"The Page FISA application incorrectly assesses that Steele did not directly provide information to Yahoo News.

"Steele has admitted in British court filings that he met Yahoo news - and several other outlets - in September 2016 at the direction of Fusion GPS."

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Democratic Leader Nancy Pelosi weighed in on the memo's release:

"President Trump has surrendered his constitutional responsibility as Commander-in-Chief by releasing highly classified and distorted intelligence. By not protecting intelligence sources and methods, he just sent his friend Putin a bouquet."

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The memo mentions onetime foreign policy adviser George Papadopoulos, who pleaded guilty in October 2017 to lying to the FBI about his Kremlin-related contacts. It also discusses texts - which have already been leaked to the media - from two FBI agents.

The memo says: "The Page FISA application also mentions information regarding fellow Trump campaign advisor George Papadopoulos, but there is no evidence of any cooperation or conspiracy between Page and Papadopoulos. The Papadopoulos information triggered the opening of an FBI counterintelligence investigation in late July 2016 by FBI agent Pete Strzok. Strzok was reassigned by the Special Counsel's Office to FBI Human Resources for improper text messages with his mistress, FBI Attorney Lisa Page (no know relation to Carter Page), where they both demonstrated a clear bias against Trump and in favor of Clinton, whom Strzok had also investigated.

"The Strzok/Lisa Page texts also reflect extensive discussions about the investigation, orchestrating leaks to the media, and include a meeting with Deputy (FBI) Director McCabe to discuss an 'insurance' policy against President Trump's election."

Confused yet? You will be.

Here’s the dramatis personae in this saga:

Russia-Trump: Who's who in the drama to end all dramas?

Compiled by a former British intelligence agent, Christopher Steele, the dossier was financed in part through the campaign of Democratic presidential candidate Hillary Clinton to dig up dirt on Trump.

It alleges that former Trump adviser Carter Page served as an intermediary between the Trump campaign and Russian government.

The Republican memo says the Steele dossier was used as evidence by the FBI to secure a wiretap of Page.

The dossier also claims the Russian government has compromising information that could be used to blackmail Trump.

However, unnamed sources have told Reuters news agency the Republican memo is misleading because, they say, all dossier excerpts used in the FBI warrant application were independently confirmed by US intelligence.

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The memo says that in September 2016 "[former British spy Christopher] Steele admitted to [justice department official] Ohr his feelings against then-candidate Trump when Steele said he ‘was desperate that Donald Trump not get elected and was passionate about him not becoming president.’ This clear evidence of Steele's bias was recorded by Ohr at the time and subsequently in official FBI files - but not reflected in any of the [Carter] Page FISA [Foreign Intelligence Surveillance Act] applications."

The memo also says that "Deputy (FBI) Director McCabe testified before the Committee in December 2017 that no surveillance warrant would have been sought from the FISC (Foreign Intelligence Surveillance Court) without the Steele dossier information."

The memo continues:

"a) Neither the initial application in October 2016, nor any of the renewals, disclose or reference the role of the DNC, Clinton campaign, or any party/campaign in funding Steele’s efforts, even though the political origins of the Steele dossier were then known to senior DOJ and FBI officials.

b)The initial FISA application notes Steele was working for a named US person, but does not name Fusion GPS and principal Glenn Simpson (founder of Fusion GPS), who was paid by a US law firm (Perkins Coie) representing the DNC (even though it was known by DOJ at the time that political actors were involved with the Steele dossier). The application does not mention Steele was ultimately working on behalf of – and paid by – the DNC and Clinton campaign, or that the FBI had separately authorized payment to Steele for the same information."