To cheers, he highlighted how people from across the United Kingdom had travelled to make their voices heard, saying: "They are saying squarely to the leadership of the Labour Party "listen to us, hear us, give us a People's Vote".
A YouGov survey of more than 1,000 Labour members for The Observer found 86% support a referendum on the outcome of Brexit talks, against just 8% who oppose it.
However, he made clear that if any vote of significance was to take place before the British people, he would prefer a general election over a second Brexit referendum.
Previous batches of papers said businesses could face red tape, customers could see higher credit card fees and patients could endure delays to medical treatment.
But shadow global trade secretary Barry Gardiner said the idea that Mrs May might call another election was "Looney Tunes territory".
"If we can not get a general election Labour must support all options remaining on the table, including campaigning for a public vote".
The phrasing was decided after a marathon late-night meeting at the conference in Liverpool.
Labour's policy is to force an election if MPs are deadlocked over Brexit.
Prime Minister Theresa May, who has ruled out a second referendum, says leaving without a deal is the only alternative to her plan that would keep Britain close to Brussels on trade - a blueprint that has been rebuffed by European Union leaders.
In what's being called a radical political proposal, Britain's main opposition Labour Party says that it would require companies to reserve one third of the seats on their board of directors for workers.
Liverpool's Jurgen Klopp talks up Chelsea title chances
It's a fact that irritates the defender and one he hopes can be altered this season. "I will not name a number of changes", Klopp said.
Mr McDonnell said: "The next leader of the Labour party has to be a woman".
However, if an election was not possible, a second referendum should be on the table.
"All the polling that we have seen is that the country is still pretty split down the middle". We want a general election.
Meanwhile, sections of the crowd could be heard shouting: "Hey Jeremy, take a note, for the many, People's Vote".
Labour politicians joined thousands of people who marched through Liverpool to urge the party to back a so-called People's Vote on the Brexit deal.
His intervention prompted an angry backlash from pro-Remain Labour MPs.
"I would like to say "Jeremy, listen to your membership and all of the people out here who would love to vote for you".
Senior Labour party member Emily Thornberry also suggested recently that she was confident that a general election would happen in the fall or in spring 2019.
It was a tumultuous summer for the Labour Party as it was gripped by allegations of anti-Semitism. They did not do this to be offered a farcical referendum on no deal or a bad deal.
"We want to make certain that those MPs that need to be called to account will be called to account", he said on Sunday. "Division, chaos and failure", Sir Keir will tell the party faithful in Liverpool. Ministers have been braced for Labour to formally reject Chequers.
A Labour spokesman said: "The point Dawn was making was that like the Thatcher government of the 1980s, this Tory Government has prioritised tax cuts for the rich while cutting services like women's refuges that save lives and keep women safe".