Boris Johnson has reportedly threatened to pull his plans for a snap general election Jeremy Corbyn said he would back an early poll.
The Labour leader told his shadow Cabinet on Tuesday morning he will support the call for an election before Christmas.
However, a No 10 source later said it could pull its early election Bill if a Labour plot that would also give the vote to 16 and 17-year-olds or EU citizens with settled status is successfully.
MPs are set to vote on a Government Bill today for an election on December 12, though it is not yet clear which date Labour will support.
Mr Corbyn said: "No Deal is now off the table so tonight Labour will back a General Election. We're launching the most ambitious and radical campaign for real change our country has ever seen.
“This is a once in a generation chance to build a country for the many, not the few. It's time.”
But Mr Corbyn’s move does not mean a December election is certain, with Labour expected to support amendments to the Bill that could lead to Mr Johnson pulling the vote.
A source in No 10 said any move to extend the franchise would be a bid to “wreck” the plans to hold a December election.
Asked if ministers would take the move of pulling the Bill, the source said: “Yes, in short.
“Nothing would sum up how broken this Parliament is if, after them all standing up there and saying they want a general election, they vote for an amendment that is deliberately designed to prevent the delivery of a general election before 2020.”
Crucial vote today
Mr Johnson will attempt to convince the Commons to vote for a December 12 election later today.
He has already been defeated on the issue three times - including on Monday evening - but today’s vote will only require a simple majority of MPs to vote in favour.
However, a December election is not yet set in stone.
Not only could Labour table amendments that might prove unpalatable to the Government - such as extending the vote to EU nationals or lowering the voting age to 16 - but the Liberal Democrats and the SNP have also appeared reluctant to accept the 12 December date.
They fear it could still allow time for Mr Johnson to bring the Withdrawal Agreement Bill before MPs ahead of the start of the campaign.
They have previously signalled support for a poll on December 9, but could put forward a proposal for an election on December 11 - which the Government is likely to accept.
A Number 10 source told the Press Association: "If there's an amendment to the 11th we could accept."
What people said
Green MP Caroline Lucas, who has been working for a second referendum on Brexit, said Labour's decision to back an early general election was "hugely disappointing".
Hugely disappointing if true. Why give Johnson exactly what he wants?— Caroline Lucas (@CarolineLucas) October 29, 2019
Election - esp under First Past the Post - won’t resolve Brexit
Many examples of majority Govt being returned on minority vote - real risk that the majority in favour of #PeoplesVote won’t have voices heard https://t.co/UlRoZYmQwQ
Labour campaign group Momentum tweeted: "Labour are officially backing an election. This is the opportunity of a lifetime to put an end to the shambolic mess the Tories have made and return hope to millions. Let's do this."
Mayor of London Sadiq Khan tweeted: "The only answer to the Brexit mess is to give the public the final say. But if there is to be a general election first, then those whose future is most affected must be given a say - including 16 and 17 year olds and EU citizens living in the UK."
Liberal Democrats shadow foreign secretary Chuka Umunna denied claims the party lobbied the speaker not to select Labour amendments demanding votes for 16-year-olds and EU citizens.
"This is categorically untrue. We have always supported Votes at 16 and for EU citizens," he tweeted.
Sheer madness to hold a General Election in December & on Boris Johnson’s agenda!— Barry Sheerman (@BarrySheerman) October 29, 2019
While many Labour figures tweeted enthusiastically about the prospect of an election, Huddersfield MP Barry Sheerman posted: "Sheer madness to hold a General Election in December & on Boris Johnson's agenda!"
Mr Sheerman also claimed: "I hear Labour frontbenchers & whips resigning over decision to vote for December election."