A senior Conservative MP has switched sides in the referendum debate on Britain's membership of the European Union, accusing the Leave campaign of misleading voters.
Sarah Wollaston, who chairs the influential Commons health select committee, had previously backed the Brexit campaign, arguing that the deal the prime minister had renegotiated with the EU did not go far enough.
But four months after backing Brexit, Wollaston said she was not "comfortable" with the official Leave campaign's claim that exiting the EU would free up £350 million to spend on the NHS, which she said "simply isn't true".
“For someone like me who has long campaigned for open and honest data in public life I could not have set foot on a battlebus that has at the heart of its campaign a figure that I know to be untrue,” she told the BBC on Wednesday.
“If you’re in a position where you can’t hand out a Vote Leave leaflet, you can’t be campaigning for that organisation.”
Wollaston said she had been concerned about the £350 million figure from the start of the campaign and told Leave campaigners in an early meeting that she would not mention it.
Now she reckons the NHS would suffer from a "Brexit penalty" because of the negative impact a Leave vote would have on the economy.
“I think right from the outset there are people within the Leave campaign who acknowledge in private that they know [the £350 million figure] is not true, but what they are trying to encourage is a discussion about the amount," she told BBC Radio 4’s Today programme. "Well, this is a kind of post-truth politics."
Vote Leave's figure of £350 million has come under sustained criticism from both the Remain camp and independent organisations. The Leave campaign claims the UK sends £50 million to the EU every day and that any money the UK gets back from the EU is decided by EU officials.
Sir Andrew Dilnot, chair of the UK Statistics Authority has said the claim is “misleading and undermines trust in official statistics”.
But Priti Patel, the employment minister and leading a Leave campaigner, hit back at Wollaston's remarks and said the campaign had always made clear that the £350 million figure is the UK's gross contribution to the UK.
"Sarah has a range of views and opinions, naturally, as a member of parliament, but I think the point to make about the £350 [million figure] is that we have been absolutely crystal-clear that that is a gross figure and importantly, that it is UK taxpayers' money that is given to the European Union," Patel told the BBC. "That is money that goes over to the European Union that we have no control over whatsoever."
A Vote Leave spokesperson said Wollaston had backtracked on comments she has made in the past. "If you compare her arguments then and now, there's been an about-turn," the spokesperson said.
"What I find quite amazing is that the language that she's using in her articles could have been written by the Remain campaign themselves, which for someone I know is an independent-minded MP is actually quite disappointing."
Wollaston's view on the economy also appears to have changed. She previously said the short-term "turbulence" of a Leave vote was balanced by the "long-term risks of remaining" in the EU, but today she said that the economic impact of Brexit would be "significant and negative" and would leave an "economy penalty" on the NHS.
The Leave camp is understood to be frustrated by the media coverage Wollaston's defection has received in comparison with the decision by a former defence secretary to quit the party over the prime minister's "tirade of fear".
Sir John Nott, who featured in Margaret Thatcher's cabinet, suspended his party membership because of David Cameron's "poisonous" campaign and said he would only rejoin if "we have a change in membership".