EU referendum: Treasury committee chairman backs Remain
Conservative MP Andrew Tyrie, who chairs the Treasury select committee, has announced he will back the Remain campaign in the EU referendum.
The former Treasury adviser said leaving the EU would almost certainly lead to a "short-term economic shock".
And he accused Vote Leave of "bribery" for saying Brexit would free up £350m more a week to go on public services.
Vote Leave's Boris Johnson defended the sum, saying it was an "underestimate" of what the UK gives to the EU.
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In a speech to the Centre for Policy Studies in Westminster, Mr Tyrie, MP for Chichester, said: "On the economic impact, most experts - among them Brexit supporters - have concluded that a short-term economic shock would almost certainly accompany leaving the EU, bringing a reduction in GDP growth.
"In practical terms, this is likely to mean somewhat lower living standards than would otherwise be the case. Most experts have concluded there would also be a long-run cost, although this is less certain.
"There are economic risks of staying and leaving, but the risks are greater to leave."
Mr Tyrie's decision comes as the Remain side hopes to focus in the final two weeks of campaigning on what it regards as the economic dangers of an exit.
His cross-party committee, which includes pro-Remain and pro-Leave MPs, recently published a report which raised concerns about two core claims by opponents and supporters of EU membership.
It criticised the Treasury for creating uncertainty among voters by failing to explain fully the calculations behind its claim that Brexit would cost households £4,300 a year by 2030 if the UK left the EU.
The MPs also said Vote Leave had been guilty of making a "highly misleading" claim that the UK contributes £350m per week to the EU.
Vote Leave is standing by the £350m figure, which is on the side of its referendum battle bus.
But Mr Tyrie was highly critical of it and it was on the latter point that Mr Tyrie reserved his strongest criticism, in his speech on Monday.
"This is nonsense politics," he said. "It is a form of electoral bribery. It is of an order of magnitude worse than usually encountered in general elections - £350m a week or £50m a day, is a false prospectus.
"It has the some of the corrosive characteristics of Tony Blair's claims on Iraq. I very much regret that the electorate has been expected to wade through this mountain of nonsense to find grains of truth."
Speaking on BBC Hereford and Worcester radio, leading Leave campaigner Boris Johnson defended the £350m figure, and said it was an "underestimate" of what the UK gives to Brussels every week.
"The last figure I saw was about £365m," he said.
He acknowledged "about half" of the money comes back from the EU, but said it was spent "under the control of EU bureaucrats".
Asked if it was a misleading claim, the former London mayor added: "You are spending the money on my behalf, you're deciding what you think I should be spending that money on.
"We don't control that money anymore and a huge quantity of it is simply wasted."
Responding to Mr Tyrie's decision to back Remain, a Vote Leave source said: "Andrew Tyrie's pro-EU views since the days of the ERM (Exchange Rate Mechanism) are well known.
"This was reflected in the disproportionate time Leave figures spent at his committee and the line of questioning. We wish him well."