(Bloomberg) -- Chancellor of the Exchequer Philip Hammond ramped up the pressure on Brexiteer Tory MPs as he warned they will trigger a long delay to leaving the European Union unless they support Theresa May’s proposed deal when it returns to Parliament.

A growing number of Tories are now backing the agreement, he said, and the deal will only be put to another vote in the House of Commons this week if the government is confident of victory. The deal was defeated for the second time on Tuesday and persuading opponents to switch is “a work in progress,” Hammond said.

“What’s happened since last Tuesday is a significant number of colleagues have changed their view on this and decided the alternatives are so unpalatable to them that they, on reflection, think that the prime minister’s deal is the best way to deliver Brexit,” Hammond said in an interview with BBC TV on Sunday. “It’s absolutely vital that we get it through next week, it’s the final chance to do this deal without having a long extension,” he said.

May has already conceded that her proposed exit date of March 29 will have to be put back and warned the delay could be much longer if Parliament refuses to back her agreement before Thursday’s meeting of the EU Council. That would mean British voters having to choose members of the European Parliament in May, an outcome that the prime minister said would be unacceptable.

“EU leaders would require a clear purpose for any extension that was not merely technical," May wrote in an article for the Sunday Telegraph newspaper. "If the proposal were to go back to square one and negotiate a new deal, that would mean a much longer extension. The idea of the British people going to the polls to elect MEPs three years after voting to leave the EU hardly bears thinking about. There could be no more potent symbol of Parliament’s collective political failure.”

While an official said last week that Tuesday was the most likely day for another vote, Brexit Secretary Liam Fox also said the deal May has negotiated will only return to Parliament if the prime minister believes she can win.

“There’s no point in having a vote if we have no chance of winning,” Fox said in an interview with Sky News on Sunday. “It would be difficult to justify.”

There was an indication of the shift among Tory MPs when Esther McVey, who quit the cabinet in protest at the prime minister’s agreement with the EU, said she will be backing the deal. While she sill thinks it’s a bad agreement, she’s come to the conclusion it’s “this deal or no deal whatsoever,” she told Sky News on Sunday morning.

Jeremy Corbyn, leader of the opposition Labour Party, said his party’s MPs are likely to be instructed to back an amendment calling for a referendum on any deal agreed by Parliament. He said he might back leave in such a plebiscite if the deal was right, setting up a clash with pro-EU members of his party.

The way he would vote in a referendum would “depend on the choice in front of us,” Corbyn told Sky News. “If we’ve got a good deal in which we could have a dynamic relationship with Europe, which was all the trading relationship and so on, then that might be a good way forward that unites the country.”

Labour has attempted to straddle the divide between those who voted remain and leave as it needs the support of voters in leave-backing districts if it is to win power. Corbyn reiterated his call for a general election and said he may move a motion of no confidence in the government if May loses in the House of Commons again.

Any referendum question “would obviously have to be a credible choice that’s real for both those that wanted to vote leave, or did vote leave in 2016, as well as those that voted remain,” Corbyn said. “Labour is unique amongst the parties in that we are appealing to people who voted both leave and remain because at the end of the day it’s the social issues facing this country, the poverty, the insecure work, the homelessness and the growing inequality that are crucial. That’s what brings people together.”

To contact the reporter on this story: Thomas Penny in London at tpenny@bloomberg.net

To contact the editors responsible for this story: Tim Ross at tross54@bloomberg.net, James Amott, Kevin Costelloe

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