The man challenging Jeremy Corbyn has gone against Scottish Labour policy to say he would not oppose a second referendum on Scottish independence.
Owen Smith, who is vying to be the next UK Labour leader, was emphatic when he told the BBC he would not obstruct a re-run of the constitutional vote.
His stance mirrors that of Scottish Labour’s deputy leader Alex Rowley, who is backing Mr Corbyn, but goes against leader Kezia Dugdale’s constitutional commitment in her party’s manifesto.
Ms Dugdale is one of Mr Smith’s most senior supporters and he strongly defended her record amid jeers from the audience during a leadership hustings with Mr Corbyn in Glasgow last week.
Asked if he would oppose a re-run of the 2014 vote, Mr Smith told the BBC: “No, of course not. If the Scottish people chose that’s what they wanted and there was agreement in the Labour Party then that would be for them to determine.”
In the wake of Brexit, Ms Dugdale reaffirmed Scottish Labour’s 2016 manifesto commitment to oppose a second independence referendum.
The manifesto reads: “We rule out another referendum on independence during the lifetime of the next Parliament.”
The claim has led to ridicule from the Scottish Conservatives, who have suggested Labour is “in a mess” amid a “lack of leadership”.
The row came as a new poll suggested Mr Corbyn is on course to trounce Mr Smith and win 62% of Labour party members’ votes.
Such a victory would see his share of vote increase by 3% from the 59% he won last year.
In the same interview Mr Smith also qualified claims made during the 2014 referendum by the pro-union Better Together campaign, of which Labour was a part.
He said promises on issues such as the UK being the best way to save the Scotland’s EU membership were “contingent” on Labour winning the 2015 election.
Mr Smith said: “All of those promises were contingent on Labour being in power and Labour isn’t in power.”
He said Labour would “be able to make good on our promises” if they were in power but fears that Mr Corbyn would leave them in “perpetual opposition”.
Mr Smith also said there should be a re-run of the EU referendum – in which Scotland voted to Remain and England and Wales voted to Leave – or a general election if the Brexit deal leaves the UK worse off.
The result of the leadership contest will be announced at the Labour conference later this month.