The BBC today accused Boris Johnson of lying after he demanded Theresa May honour the Vote Leave vow to save £350million from the EU and spend it on the NHS.
The Foreign Secretary revived the controversial claim in an explosive Brexit manifesto seen by many as a leadership.
But in a 'reality check' feature, the BBC said the figure did not add up.
Senior Brexiteer Andrew Bridgen told MailOnline the BBC should not be acting as if it was 'running the Government'.
Allies of Environment Secretary Michael Gove and Aid Secretary Priti Patel said the Vote Leave veterans were solidly behind Mr Johnson.
Sir David Norgrove, chairman of the UK Statistics Authority, today wrote to Mr Johnson saying he is 'surprised and disappointed' that he has revived the £350 million a week pledge.
The article said because of Britain's EU rebate, only £276million was sent to the European Union each week.
Reality Check editor Liz Corbin said: 'The UK's gross contribution was actually £361m, but - crucially - the rebate is removed before any money is sent to the EU. So the amount sent to the EU in 2014 was £276m per week, after the rebate.
'The Vote Leave campaign's claim argued that the money could be spent on the NHS.
'Well, it could, but that would mean cutting all the money the EU sends back to the UK, for example on farming subsidies and grants for community projects.
Mr Bridgen told MailOnline: 'I did not know the BBC were running the government and deciding spending commitments.
Mr Johnson's 4,000-word feature - which appeared on the front page of yesterday's Daily Telegraph - claimed that after Britain had 'settled its accounts' with the EU, Britain would be around £350million a week better off.
The BBC's 'Reality Check' team have been overruling politicians since the 2010 general election.
It takes issues raised by politicians in the news and drills into the detail of their claims before reaching a ruling on whether they are true.
In recent weeks, it has scrutinised anti-terror powers and checked out claims by Theresa May on police pay.
The content is designed to favour social media. It is published onto Twitter and Facebook and designed to be shared.
Since the referendum campaign, many on the Leave side - including even ex Ukip leader Nigel Farage - have accepted the policy is not deliverable.
Meanwhile, allies of Environment Secretary Michael Gove and Aid Secretary Priti Patel have told the Sunday Telegraph said the Vote Leave veterans were solidly behind Mr Johnson.
A friend of Ms Patel added: 'The principle has to be that government policy is reclaiming control of our money and that gives us the freedom to spend it however we wish on our domestic priorities, which is what she said during the campaign.
Mr Johnson has been widely condemned by Remain supporters for resurrecting the pledge, which was famously painted on the side of the Vote Leave bus during last year's referendum battle.
Liberal Democrat leader Sir Vince Cable said: 'On his central point, the £350m a week, this is a lie.
Labour leader Jeremy Corbyn said Mr Johnson's comments 'laid bare the conflicts at the heart of Theresa May's government over Brexit' and undermined the prime minister's authority.
He said: 'The foreign secretary even has the gall to dredge up the fantasy of £350m a week extra for the NHS.
The £350million a week figure was debunked during the referendum campaign by Sir Andrew Dilnot, the head of the UK statistics watchdog.
Boris Johnson was accused of 'back seat driving' the Brexit talks today as a Cabinet row exploded into public view.
Home Secretary Amber Rudd blasted 'I don't want him managing the Brexit process' and urged the Foreign Secretary to leave the talks to Theresa May.
Mr Johnson stunned Westminster with a 4,000-world article setting out his personal vision for Brexit yesterday in what many saw as a brazen leadership bid.
No 10 has scrambled to insist the Government is united less than a week before Mrs May makes a major Brexit intervention with a speech in Florence.
Ms Rudd used a major TV interview today to give a glimpse into the fury at Mr Johnson's intervention.
She famously told a TV debate during the referendum campaign she would not want Mr Johnson 'driving her home at the end of the evening'.
Ms Rudd said she had not read Mr Johnson's piece as she had 'quite a lot to do' responding to the Parsons Green terror attack.
And today she told the BBC's Andrew Marr that Ruth Davidson 'had a point' in suggesting the timing of Mr Johnson's intervention was unhelpful.
Ms Rudd added: 'I have the great good fortune to work with Boris. I know what an irrepressible enthusiast he is about Brexit and what he has done is set it out there - I think it's fine and I would expect nothing less.
'I don't want him managing the Brexit process. What we have got is Theresa May managing that process, driving the car to continue the allegory.
Ms Rudd said 'time will tell' if Mr Johnson's article was a 'helpful intervention'.