Labour MPs in pro-Brexit seats have warned Jeremy Corbyn that backing a second referendum would be "toxic" to the bedrock of the party's supporters.
Twenty-six MPs have signed a letter urging the Labour leader to "put the national interest first" and back a deal before October 31, warning a no-deal outcome would "alienate" many who supported the party at the last general election.
The letter follows poor results for the party in the European and local elections, and a narrow victory in the Peterborough by-election.
The shadow cabinet are expected to discuss the party's Brexit stance during a meeting on Wednesday afternoon.
Rother Valley MP Sir Kevin Barron, Burnley's Julie Cooper, Don Valley's Caroline Flint, and Rotherham's Sarah Champion are among the signatories to the letter.
They wrote: "A commitment to a second referendum would be toxic to our bedrock Labour voters, driving a wedge between them and our party, jeopardising our role as a party of the whole nation, and giving the populist right an even greater platform in our heartlands.
"Labour has a vital role to play fighting for a Brexit for the many, not the few. But this is a battle best fought in stage two, after the UK has left.
"Rejecting any Brexit in the hope of securing a perfect deal risks the worst outcome – a no-deal Brexit. This would further alienate many who backed Labour in 2017.
"We urge the party to put the national interest first, to back a deal before October 31."
It comes after reports that Mr Corbyn may change his party's Brexit policy and support a second referendum in all circumstances.
However a Labour Party spokesman said: "As Jeremy said after the EU election results, he's engaging in a process of consultation on our Brexit position and that will continue this afternoon at shadow cabinet."