The People’s Vote campaign, which is lobbying for a vote on the final deal Prime Minister Theresa May secures with the EU, will attempt to secure a motion on the issue at the party’s annual conference in Liverpool next month.
The group wants MPs and activists to submit a motion calling for a referendum on the withdrawal agreement with Brussels before Britain leaves in March.
At present it is not Labour Party policy to support a second referendum, but a number of senior figures have said this could change.
Shadow Brexit secretary Sir Keir Starmer has said Labour support for such a move should be “on the table”, while shadow chancellor John McDonnell has stated “we’re not taking any options off the table”.
Supporters of a second referendum argue it is necessary because although the electorate in 2016 voted for a departure, they did not vote for the final destination – what Britain’s relationship with Europe should be like outside the EU.
Opponents say it would undermine the democratic process and accuse referendum backers of trying to re-run the 2016 vote because they do not like the outcome.
The leaked memo says the cross-party group is not trying to undermine Jeremy Corbyn’s leadership by seeking a change in position.
It says: “Whatever views people have about the overall direction of the Labour Party, this campaign is not about Jeremy Corbyn and we must not – will not – use it to damage or undermine the party’s leadership or attack them personally.”
The draft contemporary resolution for Labour’s conference says the party can give the public a “clear opportunity to participate in critical decisions”.
It notes: “Conference believes that if the government’s proposed deal is unsatisfactory then the people should be allowed to express their view in a public vote on Brexit.
“The Labour movement can then unite behind Jeremy Corbyn’s determination to fight the Tories on a hard Brexit.”
The memo has been written by Tom Baldwin, director of communications for People’s Vote and a former adviser to Mr Corbyn’s predecessor, Ed Miliband.
It praises Labour’s frontbench for showing “real signs of movement” on the issue, something which should be “supported and encouraged”.
Mr Baldwin said: “It’s vital that people recognise that this is such a huge issue for our country, for the next generation, for our vital public services, for our jobs, that it’s not something that should be used for any other objective.
“Our movement, our campaign, contains people from Momentum and it contains people who’ve just resigned from Theresa May’s cabinet – it’s a broad, broad, broad campaign and people who use Brexit as a stick with which to beat Jeremy Corbyn are not serving our purposes.”
He said the memo and resolution were aimed at shifting Labour to a “sensible position which reflects the position of the vast majority of Labour Party members and the vast majority of Labour Party voters”.