RUTH Davidson has accused the Labour leadership of the “rank betrayal” of the 2m Scots who voted No in 2014 by opening the door to a second independence referendum.

She said Jeremy Corbyn and John McDonnell would “happily sell Scotland down the river if they thought it could give them a sniff of power”.

The Scottish Tory leader went on the attack after Mr McDonnell, the shadow chancellor and Mr Corbyn’s closest ally, said a future Labour government would not block Indyref2.

"It will be for the Scottish Parliament and the Scottish people to decide that,” he said.

"We would not block something like that. We would let the Scottish people decide. That's democracy. There are other views within the party but that's our view."

His comments, at the Edinburgh Fringe on Tuesday, flatly contradicted those of Scottish leader Richard Leonard, who said in March that Labour would oppose a new vote.

READ MORE: Labour 'would not block a second Scottish independence referendum'

It came hours after Nicola Sturgeon resurrected the idea of a “progressive alliance” to lock the Tories out of power at Westminster.

The First Minister, who wants a referendum by late 2020, told the Guardian: “It would not be my intention, to go into a formal coalition. I said that in 2015 and 2017 - that's not a new thing. But some kind of progressive alliance that could lock the Tories out of government.”

The Tory government has refused to grant Holyrood the power to hold a second referendum, but with Ms Sturgeon preparing to ask again, Mr McDonnell was far more receptive.

The First Minister praised his position as "basic democracy".

Mr Davidson said Labour’s “massive U-turn” on Indyref2 was part of using the SNP to parachute Jeremy Corbyn into Downing Street.

She said: “John McDonnell’s comments were met with complete dismay by Labour voters in Scotland. Today it’s becoming clear why he said it. Labour is proposing a pact with the SNP in order to parachute Jeremy Corbyn into Number Ten.

“The fact is this - Jeremy Corbyn and John McDonnell would happily sell Scotland down the river if they thought it could give them a sniff of power.

“That is a rank betrayal of the 2 million Scots - including thousands of Labour voters - who voted to stay part of the UK.

"With Jeremy Corbyn and John McDonnell doing Nicola Sturgeon's work for her, the First Minister must think Christmas has come early this year.

"Scottish voters can rest assured that the Scottish Conservatives will always stand up for our place in the United Kingdom and no Conservative Prime Minister would entertain doing a dodgy deal with the nationalists."

READ MORE: Leonard: Labour government would block Indyref2

She also mocked Mr McDonnell was referring to the non-existent “English parliament”.

She said: “I can't imagine Scotland's Labour MP's were chuffed to hear Mr McDonnell describe Westminster as an 'English parliament'. It's not. It’s a parliament for the whole UK with representatives from every corner of the country.”

Mr McDonnell’s comments provoked fury from some in Scottish Labour.

Edinburgh South MP Ian Murray called it “utterly irresponsible” and urged Mr McDonnell to clarify his remarks when he appears again on the Fringe today.