The Scottish Labour party has raised “serious concerns” about the national leadership’s position on independence.
It follows comments by shadow chancellor John McDonnell on Tuesday, which he repeated on Wednesday that he would not block a second referendum.
His position contradicted Scottish Labour policy in opposing another referendum.
Now, the Scottish Parliamentary Labour Party has issued a statement which criticises the national party.
It said: “We deplore any attempts to undermine the official policy position of the Scottish Labour Party and we express serious concerns about an apparent change in Labour’s position on a matter of vital importance to the future of Scotland and of the Scottish Labour Party itself.
“Scottish party policy is very clear – that is opposition to a second independence referendum.
“There is therefore an urgent need for the UK party leadership to engage constructively with the Scottish party leadership on the issue of the party’s stance on the future of Scotland.”
The statement added: “We are clear Labour’s position on Scotland’s future is a decision for Scottish Labour, which the UK party must accept.
“We expect all Scottish Labour MPs and MSPs to vote in accordance with party policy.”
Scottish Labour leader Richard Leonard said he spoke to the shadow chancellor on Wednesday morning to outline his position on the issue.
Mr McDonnell said on Tuesday: “I’m not being set up by Nicola Sturgeon to blame the UK government for blocking the will of the Scottish people – that’s too trite a political manoeuvre that’s been taken on at the moment.
“In the situation we’re in at the moment, my view is that we will not be blocking a proposal.
“The best way forward in all of this is to elect a Labour government. We’ll demonstrate what we can do and then I think the Scottish people won’t be interested in another referendum.
“But if they ever do come back, my view is you can’t be in a situation where you block it.”
The comments follow an opinion poll published on Monday which put support for independence at 52% in Scotland – with 48% opposed – once those who do not know how they would vote were excluded.
But Mr Leonard said his stance on a second referendum would only change if the will of the Scottish people was shown to be “demonstrably” different from 2014, when voters rejected independence by 55% to 45%.
It comes amid speculation that Labour and the SNP are moving towards some form of agreement that would see the parties join forces at Westminster in an attempt to remove Boris Johnson from Downing Street and force a general election.
However, SNP leader Nicola Sturgeon has stressed in the past that she was “no great fan of Jeremy Corbyn” and said she “can’t see the SNP going into formal coalition with Labour.”
SNP MSP George Adam criticised Scottish Labour’s position as “becoming increasingly bizarre”.
He said: “It’s hard to think of a time in recent years when they’ve been more vocal than this week’s frenzied backlash to the suggestion that people in Scotland should have a choice over their own future.
“The UK leadership recognises that democratic right – why don’t Labour in Scotland? Labour’s position in Scotland is fundamentally anti-democratic.”
Former Scottish Secretary David Mundell has, meanwhile, said Scotland should not be denied a second independence referendum if a pro-independence majority is returned at the 2021 Scottish Parliament election on a manifesto of holding a further ballot.
Speaking at a Fringe by the Sea event in North Berwick, East Lothian, Mr Mundell predicted the next Scottish Parliament election would become an effective referendum on having a further vote on Scottish independence.
He said: “If the 2021 Scottish Parliament election is fought explicitly on the issue of another referendum and there is a majority of nationalist parties then you do have to listen to that.”
Mr Mundell claimed the 2016 Holyrood election was not fought on that basis, as the independence referendum was a “subset” in the manifesto.
“If the 2021 Scottish Parliament election is fought on an explicit independence referendum basis then it is harder to push back against the idea that there isn’t a mandate for it,” he added.