Support is growing among MPs for a second referendum on Brexit.

Pro-Remain MPs could vote for a plan to attach a public vote to any deal Boris Johnson brings back from Brussels ahead of a historic sitting of parliament on Saturday.

Conservative MPs and ex-Conservative MPs are even more likely to support a referendum if Johnson is unable to secure an agreement in Brussels and asks MPs to back a no-deal Brexit instead.

But Labour leader Jeremy Corbyn dealt a blow to the chances of MPs securing a second referendum when he indicated Labour would not support the plan.

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LONDON — There is a growing belief among pro-Remain MPs that they can secure a second EU referendum next week, as doubts grow that Boris Johnson has enough support within parliament to force through any deal he brings home from Brussels.

The push for a second vote appears to be gaining momentum ahead of what could prove to be a historic meeting of parliament next Saturday, despite Labour leader Jeremy Corbyn indicating he would not support the plan.

That emergency session was called by Johnson and will be held after a crunch EU summit in Brussels on Thursday and Friday, where Johnson hopes to secure a tweaked deal to put before parliament, or ask MPs to back a no-deal exit if he is unable to secure such an agreement.

On Saturday, the chances of Johnson securing a deal which will win the support of 10 crucial MPs from the Democratic Unionist Party appeared to be in growing doubt.

Nigel Dodds, the DUP's Westminster leader, challenged key aspects of the new proposals, including the floated idea of Northern Ireland remaining in some sort of customs union with the EU.

"Northern Ireland must stay in a full UK customs union, full stop," he said.

The deal is unlikely to pass through parliament without the DUP's support because many Brexit-supporting Conservative MPs will follow the lead of their Northern Irish colleagues.

There is likely to be even more support for a referendum if Johnson is unable to strike a deal in Brussels this week, but plans for a referendum on any deal the prime minister brings back is also growing support.

Pro-Remain MPs hope to amend any motion put by the government to insist that Johnson's deal is put to a confirmatory vote, with the option to remain in the EU also on the ballot paper.

On Saturday, Labour MP Peter Kyle said that MPs would insist on putting Johnson's deal to a public vote if it delivered "less frictionless access to European markets" than his predecessor Theresa May's deal offered.

"If a deal like that is offered we will amend it so it can only come into effect after a confirmatory referendum in which the options would be to leave on those terms or Remain," he told the Observer.

"I have no doubt from soundings I have taken that an amendment to secure a confirmatory vote would be successful."

Nick Boles, the ex-Tory MP who quit over Brexit, told the Observer that he would back any deal the EU accepted but said a second referendum would be needed if Johnson was unable to secure a deal.

"I have been very reluctant to accept that a referendum might be necessary to break the logjam," he said.

"But if Johnson is unable or unwilling to agree a deal with the EU next week, we will be left with no alternative. A snap election will resolve nothing and could prolong the agony."

Corbyn warns colleagues against immediate referendum

Leader of Britain's opposition Labour party, Jeremy Corbyn, is seen during a visit to Chingford, London Reuters

But Labour leader Jeremy Corbyn dealt a blow to hopes of a second referendum on Sunday when he indicated Labour would not support the plan.

Asked by Sophie Ridge on Sky News whether MPs would be more likely to support a deal if it was put to a public vote, Corbyn said: "I think many in parliament, not necessarily Labour MPs but others, might be inclined to support it, because they don't really agree with the deal – but I would caution them on this."

He said he would instead prefer to see an election, after which a Labour-led government would renegotiate a softer Brexit deal that kept the UK in the customs union.

Corbyn's comments appear to put him at odds with many of his colleagues on the Labour frontbench.

Brexit Secretary Keir Starmer told a conference on Saturday that Labour would press for a public vote to be attached to any deal Johnson negotiated.

"Next week our priorities are clear: if Boris Johnson does manage to negotiate a deal, then we will insist that it is put back to the people in a confirmatory vote," Starmer said.

Rebecca Long-Bailey, the shadow business secretary, also indicated that she would support a second vote on any Brexit deal, telling BBC's Andrew Marrr that she "had been on a journey in relation to a public vote on Brexit, but the only option now was to let the people decide."