Labour members are to vote on keeping “all options on the table” on Brexit, including possibly campaigning for a new referendum.
Party power brokers have agreed on the wording for the conference motion on what the party should do about Brexit if it cannot get a general election.
Leader Jeremy Corbyn had previously said he would prefer the issue to be resolved by a general election.
But he has accepted he would be “bound” by the outcome of a conference vote.
‘Consensus in room’
The key delegates who decided on the motion – including shadow Brexit secretary Keir Starmer and leading figures from some trade unions – had discussed the text during a meeting which lasted several hours on Sunday evening.
And a source told the BBC’s political editor Laura Kuenssberg: “There was consensus in the room opposing the Tories’ chaotic approach to the Brexit negotiations… and that a general election should be called as soon as any deal is voted down by parliament.
“It was then agreed that if we cannot get a general election Labour must support all options remaining on the table, including campaigning for a public vote.”
The Labour Party has never formally rejected the option of a further vote, but both Mr Corbyn and his deputy, Tom Watson, have indicated they would prefer it to be resolved by a general election.
By Iain Watson, BBC political correspondent
After what I am told was six re-drafts and five and a half hours of discussion, wording that could bridge the gap between campaigners for a new referendum and a reluctant leadership was agreed.
But what was left out of the conference motion is as important as what went in.
The leadership had to agree that wording which restricted a future referendum to “the terms of Brexit” had to go.
This means that the party could, in theory, back a referendum that gave voters the option of remaining in the EU and not just a vote on the final deal.
Campaigners for a new vote see this as significant step forward.
But allies of Jeremy Corbyn say the wording doesn’t commit him to backing a referendum as it is still only “an option on the table” if Theresa May refuses calls for a general election.
So still a fudge of sorts – but one with slightly sweeter taste for supporters of a new vote who firmly believe that “all options” will become their option.
However, even the hint of a new referendum will allow the Conservatives to claim that Labour weren’t serious enough about respecting the previous one.
Pressed on the issue on BBC One’s Andrew Marr Show on Sunday, Mr Corbyn, who has said he is not calling for another referendum, said “our preference” is for a general election that would then allow a Labour government to negotiate the UK’s future relationship with Europe.
He said: “Let’s see what comes out of conference. Obviously I’m bound by the democracy of our party.”
Mr Corbyn also told the programme the UK “could be” close to a general election. Amid speculation that Labour could force a vote of no confidence in Prime Minister Theresa May if Parliament rejects any Brexit deal, he said: “We will be putting our case to Parliament and we will see what happens after that. We are absolutely ready for it.”
He said Labour would be prepared to vote down any deal Mrs May came back with, if it did not meet a series of tests Labour has set out.
However, Brexit Secretary Dominic Raab has ruled out a snap election this autumn, saying the idea was “for the birds”.
The UK is due to leave in March 2019 and Theresa May has been negotiating with other EU leaders on the UK’s future relationship with the bloc.
Talks hit a stumbling block at a summit in Salzburg on Thursday when EU leaders rejected Mrs May’s plan for Brexit – known as the Chequers agreement, and she warned them she was ready to walk away rather than accept a “bad deal”.
In a statement on Sunday, the prime minister said “many in Labour, the Liberal Democrats and the SNP are trying to thwart Brexit at every step and seeking to exploit this moment for political gain” by calling for another referendum and extending Article 50 to delay Brexit.
Labour’s conference in Liverpool began on Sunday with policy announcements on plans for worker representation on company boards and to make employers provide up to 10 days’ paid leave for victims of domestic violence.
Announcements on Monday will include:
Brexit is among eight issues to have been chosen for debate at the conference in Liverpool after a ballot by Labour members and trade unions.
The others are Palestine, the economy, housing, schools, government contracts, in-work poverty and justice for the Windrush generation.