Explaining its decision to award Vote Leave the official Out designation, Electoral Commission chief executive Claire Bassett said:

She added: We encourage all campaigners to now focus on engaging voters on the historic decision they will have to take on 23 June.”

Responding to the news, Grassroots Out congratulated rival campaign Vote Leave on securing the official designation and said it looked forward to "working closely and productively" with everyone campaigning for Britain to leave the EU on 23 June.

In a statement Conservative MP Peter Bone said GO drew its supports "from right across the political spectrum and from tens of thousands of grassroots campaigners of no particular political affiliation"-  and thanked them for their "hard work". He added:

Vote Leave and Britain Stronger in Europe have been designated as the official Leave and Remain campaigns in June's EU referendum.

Vote Leave - backed by Boris Johnson and Michael Gove - saw off a challenge from a rival campaign Grassroots Out, backed by UKIP leader Nigel Farage.

The campaigns will be allowed to spend up to £7m, get a free mailshot, TV broadcasts and £600,000 public funds.

The decision was made by the elections watchdog, the Electoral Commission.

Story developing here.

We'll be adding more clips from today's PMQs session this afternoon - you can watch them below or via the Key Video tab, or watch the whole session back via the Live Coverage tab. As we wind up our text coverage here are the key points of the day so far.

• In the first Prime Minister's Questions since the Easter recess, exchanges between David Cameron and Jeremy Corbyn were dominated by the Panama Papers tax revelations

• In other news, Culture Secretary John Whittingdale is under fire after news of his relationship with a sex worker. Labour has called for him to withdraw from press regulation decisions but Mr Whittingdale says it had not affected his decisions
• Mr Whittingdale says he broke off his relationship with the woman after he found out about her real occupation, in 2014 - before he became culture secretary
• Downing Street says the culture secretary has "the full confidence" of the PM

• Ahead of an announcement (by Thursday) of which group will be chosen as the official campaign for the Out side, Leave campaigners are warning that the eurozone is a "ticking time bomb" that will harm the UK if it stays in the EU
• The eurozone jobs crisis is encouraging more southern European migrants to head to the UK to join those from the east, according to the Migration Observatory.

Jeremy Corbyn hits back after David Cameron teases him over his tax return.

The prime minister said the Labour leader's tax form was "late, chaotic, inaccurate and uncosted" while Mr Corbyn replied that he had paid more tax than some companies owned by people the Tory leader may know.

All of their exchanges at Prime Minister's Questions were over claims about tax collection and staffing, in the UK and crown dependencies.

The Lib Dem leader has just returned the refugee camp at Idomeni on the Greece-Macedonia border and claims 10,000 children are now in the hands of traffickers.

Speaking to Jo Coburn on the Daily Politics, Tim Farron called on the UK to take in 3,000 unaccompanied child refugees.

Jacob Rees-Mogg asks David Cameron about migration figures in the government's EU leaflet that he branded a "propaganda sheet".

But the prime minister accused his backbencher of a "classic scare story" over his claims about economic migrants and UK border security.

UKIP MP Douglas Carswell gets a one word answer when he asks David Cameron about his future if the UK votes to leave the EU in the 23 June referendum.

Speaking to BBC News, Tory MP Tom Pursglove said the newspapers were right not to publish stories about John Whittingdale’s private life.

Mr Pursglove – a founder member of the EU leave group Grassroots Out – said the culture secretary probably had “more experience than anyone else in government” on press regulation. “I think we need that expertise,” he added.  

Vicki Young
Chief Political Correspondent

Image source, Reuters

Downing Street says the prime minister "has full confidence in John Whittingdale to fulfill all his duties" after Labour called on the culture secretary to take no further part in decisions on press regulation.

Asked whether the government was committed to going ahead with the next stage of the Leveson inquiry into phone hacking the spokesman said that no decisions would be made until criminal proceedings were over.

The spokesman confirmed that Mr Whittingdale hadn't told David Cameron about the relationship with a sex worker and the first the prime minister knew about the story was "about ten days ago when it began emerging on the internet".

He added that he thought the two men had now discussed the matter.     

BBC News Channel

Reflecting on this week's PMQs, BBC assistant political editor Norman Smith said it was an "old-school style", with Mr Corbyn not opting for his using "people's question time" format. The Labour leader used all his six questions on the Panama tax scandal.

Jon Ashworth, shadow cabinet minister, says Mr Corbyn's performance was "extremely effective", and adds: "I didn't think the prime minister had very good answers."

Conservative MP Tom Pursglove rides to the government's defence, saying it has "done more" than any other in tackling tax avoidance". "People should pay all the tax that they owe," he adds.

Tommy Sheppard, of the SNP, says the public are "flabbergasted at what they see as tax avoidance on an industrial scale" and claims the government is "playing catch up", adding:

Reality Check

Image source, BSIE

The claim: A leaflet being sent out by Britain Stronger in Europe says: "Jobs at risk, higher prices and your family worse off by at least £850 a year if we leave Europe."

Reality Check verdict: The £850 figure confuses GDP per household with household income, and is based on economic modelling so needs to be taken with a pinch of salt.

Read the full Reality Check here.

The World at One
BBC Radio 4

James Wharton says he disagrees with the PM's put-down of fellow Eurosceptic Jacob Rees-Mogg at PMQs, saying there is a clear "imbalance" between the UK's controls on EU immigration and immigration from the rest of the world. Asked about the government's controversial EU leaflets, he says he is "not too exercised" about them and the public are sensible enough to make their own mind up on the UK's future in the EU. But he has a dig at the worth of the leaflet, recalling one constituent telling him it is not "sufficiently absorbent for the use I want to put it too". 

The World at One
BBC Radio 4

Labour's Gisela Stuart praises Jeremy Corbyn for his "focused" questioning on tax at PMQs, claiming the PM "ducked" the issue of whether Tory MEPs were opposing measures to force firms to publish what tax they pay in individual EU countries. Conservative MP James Wharton says Conservative MEPs have their own leadership and it is up to them to decide their stance. Transparency at a national level "may be a good thing", he says, but the issue is "not black and white" and the implications need to be considered. 

The World at One
BBC Radio 4

Labour MP Gisela Stuart says she is not sure the story about John Whittingdale "adds up to very much" and she downplays the clamour from some within her party for Mr Whittingdale to stand aside from press regulation, saying she "struggles to see how this solves the problem" of the need to see the Leveson inquiry through to its natural conclusion. Ms Stuart and Mr Whittingdale are on opposing political parties but on the same Leave side in the EU referendum.

House of Commons
Parliament

Labour's motion for debate today "notes with concern the revelations contained within the Panama Papers and recognises the widespread public view that individuals and companies should pay their fair share of tax".

Labour is calling for "an immediate public inquiry into the revelations in the Panama Papers [and] HMRC being properly resourced to investigate tax avoidance and evasion".

The opposition motion calls for greater transparency about "beneficial ownership" - who really owns and profits from companies - including in the UK's overseas territories.

The World at One
BBC Radio 4

Labour's Maria Eagle tells the BBC it would be "better for John Whittingdale and better for the government" if he steps aside from matters of press regulation, saying the perception of any conflict of interest needs to be "put to rest". She says there is no question that Labour would not be pressing on the matter if the government had confirmed Leveson Part 2 - looking into relations between the press and the police - would go ahead. But Tory MP James Wharton says the story is a "storm in a teacup" and a "lot of fuss about nothing", with no evidence of wrongdoing. Mr Whittingdale has a "wealth of experience" in this area and has challenged Fleet Street in the past over the issue of phone hacking.