Party activists are set to debate a fudged motion that merely calls for "all options" to be kept on the table - which is Mr Corbyn's existing line.
Labour agreed late on Sunday night the party will vote on Tuesday on a motion committing the party to support "all options remaining on the table, including campaigning for a public vote" if no election is triggered by May's Brexit plans.
A source said the party's ruling body had agreed on the conference motion on what the party should do about Brexit if it can not get a general election. As delegates gathered, one message was emblazoned on hundreds of T-shirts and tote bags: "Love Corbyn, Hate Brexit".
Mr Corbyn told an eve-of-conference rally in Liverpool: "If this Government can't deliver, then I say to Theresa May: the best way to settle this is to have a general election".
A YouGov survey of more than 1,000 Labour members for "The Observer" found 86pc support a referendum on the outcome of Brexit talks, against just 8pc who oppose it.
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.
Jeremy Corbyn, as I understand it, wasn't in the meeting when the decision was taken but was at a party rally.
"We would vote it down if it didn't meet our tests in order to send the government, if it is still in office, straight back to the negotiating table and if there is a general election and we are in office we would go straight to the negotiating table". Jeremy Corbyn's foolish and misguided decision to spend an entire summer baiting the British Jewish community appears to have backfired drastically, and turned thousands of vital swing voters away from the Labour Party.
"We're not ruling out a people's vote, but there's a real risk, and I think people need to take that into account when we're arguing for one". Obviously I am bound by by the democracy of our party'.
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.
Tottenham MP David Lammy and peer Lord Adonis were among the speakers while MP Luciana Berger led the march. It calls for Britain to leave the EU but remain in the bloc's customs union with "full access" to the EU's huge single market.
The Labour leader said today that he would prefer forcing a general election this autumn instead of a second referendum but promised to "adhere to what members want".
Mr McDonnell was confident Labour could negotiate a good deal with Brussels by 29 March 2019, the date when Article 50 runs out and Britain leaves the European Union.
Andrew Adonis, a Labour member of the House of Lords who supports holding a second referendum, said Labour can't sit on the sidelines while the country staggers toward political and financial chaos.
He has always been a critic of the EU's free-trade policies and must also find a way to reconcile the traditional working-class wing of his party, who mostly voted for Brexit, and his own army of younger supporters that want to stay in the bloc.
A tacit agreement to try to offer her some support before she heads to what is going to be a hard annual conference of her governing Conservative Party later this month was broken by some British diplomatic missteps.
McDonnell's caution is likely to disappoint Labour members pushing for a second referendum.