JOHN McDonnell has insisted a Labour Government would not block a second independence referendum.

The shadow chancellor said the issue would be for the "Scottish Parliament and the Scottish people to decide".

He made the comments during an interview at the Edinburgh Fringe with LBC broadcaster Iain Dale.

It came the day after a poll showed support for Scottish independence has risen to 52 per cent, with 48% against. Among Labour supporters, a third said they would vote Yes.

Scottish Labour leader Richard Leonard has repeatedly said his party would refuse to grant a Section 30 order to give Holyrood the power to hold another vote.

READ MORE: Leonard: Labour government would block Indyref2

But Mr McDonnell flatly contradicted this. He said: "It will be for the Scottish Parliament and the Scottish people to decide that.

"They will take a view about whether they want another referendum. Nicola Sturgeon said by late next year or the beginning of 2021.

"The Scottish Parliament will come to a considered view on that and they will submit that to the Government and the English Parliament itself.

"If the Scottish people decide they want a referendum that's for them."

He added: "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."

In March, Mr Leonard insisted a Labour government "would not agree to a second independence referendum emerging from either the Scottish Parliament or from any other quarters".

Ian Murray, the Labour MP for Edinburgh South, reacted furiously to Mr McDonnell's comments, insisting they are "utterly irresponsible" and "betray our party’s values".

He said: "The Labour Party is an internationalist party founded on a vision of solidarity and we should never seek to appease nationalists - whether they be for Brexit or Scottish independence - who want to divide communities and people.

"John McDonnell has even bought into the nationalist narrative that Westminster is an ‘English Parliament’, in an insult to the hard work carried out by Scottish MPs from every party.

"We were promised by the SNP that the 2014 referendum was once-in-a-generation, and we have a duty to hold the Nationalists to their promise by firmly opposing a divisive second independence referendum.

"But one of the architects of the Corbyn project that is destroying the Labour Party now appears willing to destroy our United Kingdom with thoughtless rants at the Festival."

Speaking at the Fringe event, Mr McDonnell blamed nine years of austerity and the prospect of a Boris Johnson Government for boosting support for independence.

But he dismissed the idea of any coalition or arrangement with the SNP at Westminster if Labour fails to secure a majority in a snap election.

He said: “My own view is I think we will have a majority. If we are a minority government, we’ll form a minority government.

“We’ll seek to implement our manifesto, and we’ll press on that in Parliament.

“We’ll expect the other opposition parties, or other MPs as well, to vote for those policies and if they don’t we’ll go back to the country.

“I give this warning to other parties: if they want to vote against a real living wage, if they want to vote against £70 billion being invested in Scottish infrastructure, if they want to vote against the Green industrial revolution tackling climate change, so be it.

“We’ll go back to the people and let them explain to the people why they won’t support those policies."

Mr McDonnell also ruled out Labour joining a government of national unity to block a no-deal Brexit.

He insisted there is still time to prevent no-deal, but said the party would not enter into "coalitions or pacts".

Read next: Ruth Davidson warns 'millions' can't afford shock of a no-deal Brexit

Labour's UK leadership has repeatedly undermined the position of the Scottish party on a second independence referendum.

However, Labour not blocking a referendum would not necessarily guarantee it.

In theory, Labour MPs could abstain in a Commons vote on a Section 30 order and if the other parties rejected it, they could attribute that to parliamentary democracy too.

Only the active cooperation of the UK government would ensure Indyref2.

But the SNP could argue that allowing Westminster to vote down a Section 30 order would be tantamount to blocking a referendum, and a breach of Labour's promise.

A Scottish Tory spokesman said: "From top to bottom, Labour is incredibly weak on Scotland’s place in the UK. We all know Nicola Sturgeon’s condition for support in Westminster would be green-lighting a second independence referendum.

"Now it seems John McDonnell is very happy to pay that price. Yet again, it shows only the Scottish Conservatives can be trusted on the Union."

Scottish Liberal Democrat leader Willie Rennie said Mr McDonnell's comments were "astonishingly irresponsible and not in the interests of Scotland or the UK".

SNP MSP George Adam said: "It is for the Scottish people to decide upon their future. The Scottish Government has a crystal clear mandate to give them that choice.

"Polling this week shows that they want that choice sooner rather than later - with a majority in favour of the opportunities of independence.

"For any Westminster government to deny that would be a democratic outrage, and Tory posturing on the issue is completely unsustainable.

“We trust this position will now receive the fulsome backing of Richard Leonard and Scottish Labour.”

Former Scottish Labour MP Pamela Nash, chief executive of Scotland in Union, said: "The Shadow Chancellor is right to say that Scotland’s future is in Scotland’s hands – and we have chosen to remain in the UK.

“That does not mean that we should have another divisive referendum so soon after a once-in-a-generation contest, and the very last thing Scotland needs is another layer of constitutional chaos.

"Labour’s 2017 General Election manifesto was clear that the party opposes another referendum.

“It is also deeply disappointing to hear that the Shadow Chancellor does not appear to understand that Scottish people are fully represented in two parliaments.

"The House of Commons is where representatives of England, Scotland, Wales and Northern Ireland come together to work in the interests of everyone in the UK.”