The UK is on course for a December general election after Labour announced its conditions to back the move had been met.
Jeremy Corbyn told his shadow cabinet Labour would launch the "most ambitious and radical campaign for real change our country has ever seen" now a no-deal Brexit was "off the table".
It comes ahead of the British government's bid to convince MPs to back a poll on December 12.
Mr Corbyn told his top team on Tuesday morning: "I have consistently said that we are ready for an election and our support is subject to a no-deal Brexit being off the table.
No Deal is now off the table so tonight Labour will back a General Election.
— Jeremy Corbyn (@jeremycorbyn) October 29, 2019
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.
"We have now heard from the EU that the extension of Article 50 to January 31 has been confirmed, so for the next three months, our condition of taking no-deal off the table has now been met.
"We will now launch the most ambitious and radical campaign for real change our country has ever seen."
Boris Johnson will attempt to convince the Commons to vote for a December 12 election at his fourth time of asking on Tuesday using a short Bill which sets aside the Fixed-Term Parliaments Act, requiring only a simple majority of MPs.
However the Liberal Democrats and the SNP are reluctant to accept his date - fearing it allows time 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 said: "If there's an amendment to the 11th we could accept."
But Mr Corbyn's move does not mean a December election is certain, with Labour expected to support amendments to the Bill.
Other amendments reflecting their policy, such as votes for 16 and 17-year-olds, are being considered.
The party is understood to back a change to the proposed date which, if such an amendment is selected by the Speaker, could be backed by the Liberal Democrats and the SNP.
Earlier on Tuesday, Lib Dem MP Chuka Umunna said his party is against holding a general election on Mr Johnson's preferred polling date of December 12, telling BBC Radio 4's Today programme: "It cannot be the 12th."
However, Mr Umunna signalled the Lib Dems could be flexible over their own preferred election date of December 9.
He said: "We will see what else they come forward with. We have got to break the gridlock."
The one-page Bill - titled the Early Parliamentary General Election Act 2019 - published by the Government, sets the date of the proposed general election as December 12 2019.
