In a stark warning issued ahead of this morning’s showdown at the Labour conference in Liverpool, Ian Murray said Mr Corbyn’s backers risked “shutting down” the Scottish party.
Delegates from unions Unite and Aslef were both expected to oppose the package of measures because they include proposals to introduce two new seats for nations on Labour’s National Executive Committee, with the positions appointed by party leaders in Scotland and Wales.
Mr Corbyn’s supporters fear the new roles would tip the balance of power on the executive against him. The newly re-elected Labour leader has made half-a-dozen attempts to block or delay the move via procedural manoeuvres in the past four days.
The power struggle resulted in a fiery showdown with Scottish Labour leader Kezia Dugdale at the weekend, and yesterday morning the Welsh First Minister Carwyn Jones insisted the measures be put to a vote of party members without change or delay.
Mr Murray told a fringe meeting in Liverpool that after years of attempting to boost Scottish Labour’s powers to dispel the perception it was a “branch office” of the UK party, failure to pass the changes to the party’s constitution would be a gift to the SNP.
He said the “branch office” tag that the party has in Scotland had “completely destroyed” it, and said reforms that include giving Scottish Labour power over Westminster candidate selection were “utterly critical” in rehabilitating the party’s image.
His comments came as Neil Findlay MSP, who ran Mr Corbyn’s campaign in Scotland, made an impromptu appeal to Labour delegates not to be “seduced” by the idea the SNP is a progressive party.
Attempting to dissuade colleagues of the idea the Nationalists could help form a progressive alliance to put Mr Corbyn in Downing Street, Mr Findlay said: “You can’t pay your bills with a Saltire.”
Telling delegates he wanted to deliver a “few home truths”, Mr Findlay said: “I had to come here today with some words of warning and some words of caution for my friends here in England and across the UK.
“It’s a friendly warning to my brothers and sisters because some people are being seduced – seduced into believing that the Scottish National Party is a party of the left, a party that is progressive and a party that we should be doing deals with.”
Highlighting comments by the First Minister that the case for independence trumped concerns over the economy and Scotland’s place in Europe, Mr Findlay added: “Why would we do a deal with a party that wants to divide us on the basis of nation instead of uniting us on the basis of our class?
“In Scotland, the attainment gap in schools is growing, our social care system is on the brink, our NHS is under pressure like never before.
“But last week, in the Herald newspaper, Nicola Sturgeon said independence transcends all of that.”
He added: “Don’t judge the Nationalists by their rhetoric, judge them on their failure to protect our essential services.”
Today’s vote is expected at about 9am.
Len McCluskey, the Unite general secretary who controls the largest bloc of union delegates at the Labour conference, said the proposals put him in a “difficult position” and refused to rule out voting down the entire package.
Labour sources are confident the reforms will pass with the help of supportive unions, but the decision relies on enough ordinary delegates attending the session.
Mr Murray said: “If certain people on the National Executive Committee run a campaign to vote these rules down tomorrow they are in danger of not just not helping the Scottish Labour party, they are in danger of shutting the Scottish Labour party down.”
Mr Murray said Labour lost the general election in 2015 because David Cameron set Scottish nationalism against English nationalism, and said the party’s own analysis made clear the danger of considering an SNP pact.
“That’s what all the analysis has told us,” he said.
“The reason that a lot of members of the Labour party and Labour supporters don’t know that analysis is because the party has been refusing to release it.”
He added: “We are a broad church of a party and we always have been and I will not be leaving the Labour Party.”