Labour and the Conservatives would be wiped out in Scotland at a general election if they do not back a public vote on any Brexit deal, according to polling analysis.
The SNP would win all but the Lib Dems' four seats in Scotland, with Scottish Labour forecast to haemorrhage 40% of their 2017 votes if an election was held now.
Analysis of polling for pro-EU campaign groups Best for Britain and Hope Not Hate found that Labour would lose three votes to remain-supporting parties for every one it would lose to the Brexit Party.
Scottish Labour is due to decide whether to commit to backing a second referendum in all circumstances, as supported by leader Richard Leonard.
A decision on the policy will be made by the party's Scottish Executive Committee at a meeting in Glasgow on Saturday, with sources close to Mr Leonard suggesting he is confident members will back a confirmatory vote with an option to remain.
Pressure mounted for Labour to clarify its position on Brexit following a poor showing at the European elections which saw the party slump to fifth place with just 9.3% of the vote, lose both its MEPs and caused two frontbenchers to resign.
With the polling pointing towards Labour being without any Scottish MPs for the first time in almost 100 years, campaigners have used the new polling to renew calls for Scottish Labour to unequivocally push for a second EU referendum while supporting remain.
Best for Britain chief operating officer Naomi Smith said: "The consequences of Labour's ambivalent policy towards a final say on Brexit looks set to hurt them further. They're expected to lose almost half of their 2017 vote share, according to our analysis.
"The Labour leadership now needs to pick a side, and that can start with the Scottish Labour executive committee voting to become a party of remain.
"It's obvious which position Labour should take if it wants to be in government, and Scottish Labour leader Richard Leonard can demonstrate leadership on this for the entire UK party."
According to analysis of the voting intentions of from 15,231 survey respondents, only 57% of people who voted Labour in 2017 said they would do so again in a new election. Some 30% would vote for remain-supporting parties, with 19% going to the Lib Dems, 9% for Greens and 2% to Change UK. A further 2% would support the SNP - or Plaid Cymru in Wales - while 10% would go to the Brexit Party.
Nick Lowles, Hope Not Hate CEO, said there is a majority for parties against a no-deal Brexit, but warned that Labour "is bleeding votes to parties that have taken a clear anti-Brexit stance".
Mr Lowles added: "This poll reveals a quite shocking surge in a hardline right-wing Brexit Party, led by a divisive and dangerous politician in Nigel Farage.
"A hard Brexit, or a no deal Brexit, would cause untold damage to those communities where the far right wants to stir up division.
"Labour will lose seats in areas that voted Leave if they continue to lose the support of Labour remain voters. It's counter-intuitive but it's the reality.
"The evidence is clear - from this poll, and the recent election results - if Labour wants to win a majority at the next election, it needs to move to keep its Remain voters on board."