Labour’s Ian Murray has heavily criticised party leader Jeremy Corbyn and went as far as to claim he would cost them any upcoming general election.
The Scottish MP lamented the fact that members at the party conference in Brighton rejected a call to come out in favour of staying in the European Union.
Mr Corbyn has promised a government he leads will negotiate a new Brexit deal and put it to a referendum – but neglected to say how the party should campaign in that public vote.
Speaking on BBC Radio Scotland on Tuesday, Mr Murray criticised the “debacle” and claimed there were two reasons the party was failing – with Mr Corbyn being one of them.
He said: “I think there’s two things that would cost the Labour Party the election at the moment and the polls and the people are telling us what they are.
“The two things are the ambiguity and the constructive ambiguity of Brexit which is one thing, and the second thing is the leader of the Labour Party.
“Let’s just be completely honest about that.
“His personal approval ratings are minus 65, they’re the worst in history of any opposition party.
“I knock on doors week in, week out and people tell me that is the impediment to people thinking about supporting the Labour Party.
“The polling at the moment has the Labour party either level pegging with the Conservatives or 15 points behind.
“I suspect the Labour Party, in the current issues with the country and where the current Prime Minister is, we should be 20 points ahead, looking at a credible alternative government.
“We’re not. People have to ask themselves why and I think the debacle that happened at conference yesterday just highlights the fact why we’re not 20 points ahead.”
Monday’s movement at conference came after Scottish Labour leader Richard Leonard also called for clarity in the party’s position.
The Scottish executive of the party previously backed his proposal calling for an affirmative vote and he added he would support Labour taking a remain stance.
Mark Drakeford, leader of Welsh Labour, also set out his stall for a campaign to remain, claiming up to 50,000 jobs could be lost in the country by a “crash-out Brexit”.
But Mr Leonard reaffirmed his support for ally Mr Corbyn who on Sunday vowed to serve a full term as prime minister if the party wins the next general election.
Mr Murray added: “I think the important thing yesterday is to acknowledge the fact that we want and most people want in the Labour Party movement to revoke Article 50 and remain in the EU.
“The way you do that, the journey towards that, is through a people’s vote with the option to remain. We’ve got to that position which I think’s a big step forward but I think the rest of the position is rather ludicrous.
“I think the SNP, Liberal Democrats and the Scottish Labour party – and most of the Labour Party movement – want the same thing. It’s the journey to get there.
“And I think the important thing from yesterday and the important thing in this entire debate is to get that parliamentary majority, to get that public vote with an option to remain onto the legislation so we can take this back to the public.
“I think the issue of whether you go back to the country with a public vote on the EU referendum issue will happen before a general election.
“Quite frankly if Jeremy Corbyn, given his unpopularity ratings across the country, wants to stay neutral I’m not sure that’s a bad thing for the Remain campaign.”