That's it from us on this subject for today.

Our contributors were Dulcie Lee, Jennifer Scott, Kate Whannel, Megan Fisher, Arryn Moy and Alex Kleiderman.

Have a good evening, and remember there's always more to read on our politics page - here.

Image source, PA Media

It was a dramatic first day after the Easter break, with Boris Johnson addressing MPs for the first time since becoming the UK's first sitting prime minister to be sanctioned for breaking the law.

What happened?

• Johnson repeated the apology he made on camera last week for attending a birthday gathering thrown for him
• He denied deliberately misleading MPs and said he didn't knowingly break the rules
• Labour leader Sir Keir Starmer said his apology was "mealy-mouthed" and accused him of giving absurd excuses
• The Lib Dems, Labour, SNP and SDLP all called for Johnson to resign

• Tory MP Mark Harper said Johnson's actions were indefensible and submitted a letter of no confidence in him to the 1922 committee

What next?

• On Thursday, MPs will debate a motion on whether or not to refer the PM to the privileges committee
• If it passes, the committee will consider whether Johnson knowingly misled MPs, and could recommend a sanction. MPs would then vote on whether to accept the committee's recommendations
• Meanwhile, the police investigation into alleged gatherings continues

Want more?

• Read our full round up of the day in our main story here
• Will the PM face more fines? We've calculated the odds

Jennifer Scott
Political reporter, BBC News

Image source, PA Media

So far, more than 50 fines have been issued for breaking Covid laws in No 10 and Whitehall.

The BBC is aware of three events that have led to fines so far.

But the Met Police's investigation is into 12 events in total - meaning there are nine more gatherings that could result in sanctions.

The prime minister is known to have attended at least two of these, and reports suggest he could have been at up to three more.

So in theory, Mr Johnson could face more fines, depending on the outcome of the police investigation.

The PM has promised to get back to focusing on voter priorities - including the cost of living crisis and the war on Ukraine.

But will his determination overcome any future twists and turns in this saga, whether it be fines or further damning details?

Read more here.

Let's get a final bit of reaction to today's events from the Covid-19 Bereaved Families for Justice UK group.

They say the PM's apology sounded like "the words of someone who is sorry they’ve been caught, not someone who regrets the harm they’ve done".

In a statement on Twitter, external the group say his defence that he didn't knowingly break the rules was laughable.

"Backbench Tory MPs might want us to move on from Partygate, but first they’ll need to move Johnson on from his office," they say.

Also earlier, Plaid Cymru's Westminster leader Liz Savile Roberts described the PM as "a millstone round his government's neck".

"The PM debases himself, debases his office and debases his government," she said.

We're just going back over a bit more of what was said in the Commons earlier, and SDLP MP Colum Eastwood said the PM and chancellor were "partying in Downing Street" while his constituents were "watching through care home windows as their parents died".

"We know he has no respect for the public but show us he has some respect for himself and please, please, please resign now."

More now from Conservative MP Mark Harper, who earlier told the Commons that Boris Johnson was no longer worthy of the "great office" he holds.

Explaining his decision to submit a letter of no confidence in the PM, the former chief whip tells the BBC many people made extraordinary sacrifices to obey lockdown laws.

Harper says all his Conservative colleagues are going to have make a decision soon about whether they want Johnson to continue.

"I'm not expecting lots to follow me today, but they're going to have to reflect in the coming days and weeks," he says.

"I think many of them will reach the same conclusion that I have."

Image source, Reuters

Just a little aside...

When MPs head to the Commons on Thursday to debate the actions of Boris Johnson, and whether they merit a referral to the Privileges Committee, the prime minister will be nowhere near the chamber.

Instead, he will be Ahmedabad, India, as he begins a visit to the country to bolster trade.

Johnson will then travel to New Delhi on Friday to meet Indian Prime Minister Narendra Modi.

We do understand the PM will be in the House for Prime Minister's Questions on Wednesday before his trip though.

Boris Johnson's time at the despatch box has now come to an end. Oppostion MPs have been coming with call after call for his resignation.

Johnson will address Tory backbenchers behind closed doors at 20:00 BST.

Image source, UK Parliament

The Green Party's Caroline Lucas asked earlier what could be done to protect the ministerial code - the rulebook on behaviour issued by the PM - "when the person who is entrusted with guarding it breaks that code".

The Brighton Pavilion MP then quoted a historian who recently described Johnson as a "rogue prime minister".

Johnson said he didn't agree with the "characterisation" and reiterated that he had explained and apologised.

We found out earlier that MPs will get to vote on Thursday on whether Johnson should be investigated for knowingly misleading Parliament in his past statements about No 10 parties.

Iain Watson
Political correspondent

While one new letter of no confidence in Boris Johnson has gone in today, most non-Ukraine contributions from the Conservative benches have welcomed the PM’s repeated apologies - though the former minister Steve Baker, a Christian, wanted more than that: repentance.

Significantly, while he has organised many succesful rebellions against his own party leaders, he did not join fellow Covid Recovery Group member Mark Harper in calling for the current leader to go.

As we type, Boris Johnson is still in the House of Commons answering questions from MPs in his first appearance since being fined for breaking lockdown laws.

Here is a quick re-cap of what we have heard so far:

• The PM repeated his apology that he made on camera last week for attending a birthday party thrown for him in the Cabinet Room in June 2020 during the first lockdown
• But he said the hurt and upset caused by the rule breaking made him more determined to lead on the British people's priorities, including on Ukraine and the cost of living crisis
• Labour leader Sir Keir Starmer called his statement "a joke" and "mealy mouthed"
• Starmer repeated his call for the PM to resign, and urged Tory backbenches to oust him if he won't
• The SNP and Lib Dems also called for Johnson to go
• Many Tory MPs backed Johnson, especially over his actions in helping Ukraine
• But the Conservative former chief whip, Mark Harper, said the PM was "no longer worthy of the great office he holds" and tweeted a letter of no confidence

A little earlier, Tory MP Julian Lewis asked if the prime minister had the power to make senior civil servant Sue Gray publish her full report into the parties in Downing Street during lockdown.

You may remember Boris Johnson ordered her to carry out an inquiry - but its full publication was paused by the police investigation.

Lewis said publishing it "would put an end to this matter" and stop the government being "diverted away" from helping Ukraine.

Johnson said the Metropolitan Police should conclude its investigation before such a report is published.

"The public have made up their minds. They know what he is," Labour leader Sir Keir Starmer says.

Watch his verdict on Johnson's apology below.

Tory MP Michael Fabricant, who has defended the PM throughout the Partygate row, says he is desperately sad to hear about his own constituent referenced by the Labour leader in his speech.

He describes how his best friend's mother died in hospital without them by their side, and notes that the PM's mother also died during the pandemic.

"We've all suffered from these heart-wrenching tragedies," he adds, "and none of us should forget it."

But it seems his support is still firmly with Boris Johnson.

Conservative Steve Baker says the prime minister "could not have made a more humble apology".

He says the PM also needs to show repentance and asks for an assurance that "nothing of this kind will ever happen again".

Boris Johnson repeats his apology.

The DUP's Sammy Wilson says the PM's apology was genuine.

He adds it is important to focus on the future rather than the past.

He asks Boris Johnson what discussions the PM has had about the weaponry Ukrainians need to drive back the Russians.

Johnson says the UK is in continuous discussions with Ukraine.

Tory backbencher Peter Bone points to the announcement earlier that MPs will vote on Thursday on whether to refer the PM to the privileges committee.

He says there is only one issue in question for such an investigation - "Did the prime minister deliberately mislead the House [over the parties]?"

Bone asks Johnson the question directly.

The PM answers: "No."

Iain Watson
Political correspondent

The former chief whip Mark Harper delivers a blow to the PM - says he is not fit for high office.

So far he has kept his powder dry but as a formidable organiser, this intervention could yet be significant.

Many other Conservative critics have bitten their tongues during the Ukraine conflict.

More on former chief whip Mark Harper, who confirms on Twitter that he's submitted a letter of no confidence in the prime minister.

In the letter, he says Johnson is "no longer able to deliver the principled leadership required to take our country forward".

Tory MPs can trigger a leadership contest if 54 letters of no confidence are sent to Sir Graham Brady, who chairs a committee of backbench MPs known as the 1922 Committee.

There's no official running tally of how many letters have been submitted - they have been triggered by various issues over the course of Johnson's leadership - the only way we'll know for sure is if that crucial threshold of 54 letters is reached.