A banner is unfurled before Jeremy Corbyn’s address to the Labour Live event earlier this month.

A pro-Corbyn group is to launch its own drive for a “people’s vote” on a final Brexit deal, with the aim of persuading leftwing Labour members concerned about backing a cross-party campaign.

The grassroots Labour for a People’s Vote group, which is led by several former Momentum figures, as well as trade union leaders, has the backing of more than 60 constituency Labour parties (CLPs) to try to force a vote at this year’s party conference to change Jeremy Corbyn’s Brexit policy.

The group will call for Labour to oppose the government’s final Brexit deal, which the party has said it would do if the deal with the EU did not meet six tests set by the shadow Brexit secretary, Keir Starmer. The group will then campaign for the party to go further and campaign for a public vote on the deal with an option to stay in the EU should voters reject the deal.

Activists from 62 local Labour parties have pledged to raise the issue in a motion at the party’s conference this September, which the group said was a major shift among the Labour grassroots members, the majority of whom are Corbyn supporters.

More than 100,000 people joined the people’s vote march through central London on Saturday, fronted by Labour’s Chuka Umunna, the Conservatives’ Anna Soubry, the Greens’ Caroline Lucas and the Liberal Democrat leader, Vince Cable.

Corbyn did not attend the march and Labour’s position on Brexit was subject tocritical chants from the crowd, who sang: “Where’s Jeremy Corbyn?”

Labour activists involved in the parallel drive for a people’s vote on the final deal believe in the need for leftwingers to have their own campaign, which does not disparage Corbyn.

“It is essential that there is clear red water between the mainstream centrist remain campaigns…