Boris Johnson has abandoned his “do or die” pledge to leave the EU by 31 October and will plead with MPs next week to give him a pre-Christmas general election.

The prime minister wrote to Jeremy Corbyn on Thursday night saying he would give parliament one last opportunity to scrutinise his withdrawal agreement bill and “get Brexit done” by 6 November. But he will also table a motion under the Fixed-term Parliaments Act next Monday asking for an early general election. It will require the backing of two-thirds of MPs to succeed.

Play Video 0:43 Jeremy Corbyn: Labour will back general election if Johnson takes no-deal off the table - video

Johnson’s letter says: “An election on 12 December will allow a new parliament and government to be in place by Christmas. If I win a majority in this election, we will then ratify the great new deal that I have negotiated, get Brexit done in January, and the country will move on.”

Boris Johnson (@BorisJohnson) I have written to Jeremy Corbyn: this Parliament must get Brexit done now or a NEW Parliament must get Brexit done so the country can move on pic.twitter.com/PekfFRsR9F

Downing Street sources claimed that if MPs reject Johnson’s request, he will pull the withdrawal agreement bill and continue “campaigning” for a general election every day. “We will not allow MPs to continue holding this country hostage,” the source said.

Labour appear to be poised to reject the government’s request, but Jeremy Corbyn told the BBC on Thursday night that no final decision would be made until the EU27 has agreed a Brexit delay. “We’ll know tomorrow what the extension will be and I can answer that question tomorrow. What I’m saying now is: take no deal off the table,” he said.

Corbyn also denied that Labour’s position on a general election was confused, given that the party had consistently said it wanted voters to go to the polls to oust the Tories.

He said: “We are not resisting the chance to have an election. We want an election because we want to take our case to the people of this country but we do not want this country to be in any danger of crashing out of the EU without a deal because of all the damage that will do to jobs, services and trade all over this country.”

The EU’s plan to offer on Friday an extension up to 31 January is expected to be put on hold until as late as Tuesday. Sources said it remained the most likely outcome, but that the dramatic developments in Westminster needed to be fully understood and the choreography in Brussels could change.

The Corbyn-supporting campaign group Momentum urged the party to back an election, saying: “Bring it on.”

But several shadow cabinet members claimed that a decision had already been made to abstain.

One described a yes vote as “unwhippable” because of the concerns of many Labour MPs about campaigning in the cold and dark. “There’s an absolute, quiet defiance,” he said. “We’re not going to go out and campaign in the bleak midwinter.”

One Labour MP said: “I don’t think the party will go for this. It’s a dead cat because he hasn’t achieved his “do or die” or “dead in a ditch” promise on leaving by 31 October. You can’t put off democracy because it’s dark nights, but we do need to think very carefully in this climate about having to go out and campaign in the dark.”

Some members of the shadow cabinet met to decide how to respond on Thursday afternoon – but others, including Ian Lavery and Jon Trickett, who are keen supporters of an early election, were not invited, in what was described as an oversight. Both were said to be furious.

Johnson had previously said he would wait for confirmation from Brussels of the Brexit delay that he reluctantly requested on Saturday before deciding on his next steps.

He sent a letter asking for an extension to article 50, as the Benn act required, after MPs refused to fast-track his deal through parliament in time for the 31 October deadline.

The election motion will need the support of two-thirds of the Commons, equating to 434 MPs.

Johnson told Sky News: “The way to get Brexit done is I think be reasonable with parliament and say if they genuinely want more time to study this excellent deal, they can have it, but they have to agree to a general election on 12 December and that’s the way forward, because this parliament has been going on for a long time without a majority.

“It’s refusing to deliver Brexit. It’s impossible to deliver legislation. It’s time, frankly, the opposition summoned up the nerve to submit themselves to the judgment of our collective boss, which is the UK.”

Earlier, Johnson met his cabinet, some of whom, including the Northern Ireland secretary, Julian Smith, were reluctant to support the idea of entering into a general election campaign without yet having left the EU.

The Brexit bill passed its second reading in the Commons on Tuesday by a larger than expected majority of 30 and Smith believed that would be sufficient to carry it through all its stages in parliament. But some of his colleagues, including the chancellor, Sajid Javid, feared that the majority could easily melt away, so they encouraged Johnson to head straight to the polls.

Javid’s first budget, which was slated for 6 November, is now expected to be cancelled.

Labour twice blocked the prime minister’s plan for a mid-October election, warning that Johnson could use the period during which parliament was suspended to take the UK out of the EU without a deal.

Jacob Rees-Mogg, the leader of the House of Commons, told MPs the government was willing to make as much time as possible available to MPs to scrutinise the Brexit legislation – if parliament agreed to an election. “We are willing to start work tomorrow, Mr Speaker, if you are willing to recall parliament,” he said. “We are willing to work 24 hours a day between now and 6 November.”

After reaching a fresh deal with the EU27, the prime minister had hoped to fast-track it through parliament in time to leave by Halloween. But while MPs supported the principle of the bill on Tuesday, they rejected his blistering timetable.