JOHN McDonnell has promised that a Labour Government will not block a second referendum on Scottish independence.

The comments will cause dismay among Scottish Labour, and will embarrass Richard Leonard, who last year insisted opposition to indyref2 would be in the party's next manifesto. 

Speaking at the Edinburgh Festival Fringe, McDonnell told LBC host Iain Dale that the issue would be for the "Scottish Parliament and the Scottish people to decide".

He added: "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."

Last year, speaking at the party’s conference, Leonard insisted his party would stand on a platform opposing a new vote.

He told delegates: "We don't need another independence referendum to change Scotland, as far as I am concerned – we've just had one.

"The majority of people do not want one, and as we meet here this week with the prospect of a general election, I can make clear today that the next Labour manifesto will oppose another independence referendum."

In March of this year, he even said a Labour government would refuse to grant a "Section 30 order".

He told the BBC Sunday Politics Scotland: “What we said in the manifesto at the 2017 election was that there is no case for, and we would not support, a second independence referendum.”

Pressed on Labour ruling out a Section 30 order and blocking a new vote, he said: “We will not agree to a second independence referendum. There’s no appetite for it.

“A Labour government... would not agree to a second independence referendum emerging from either the Scottish Parliament or from any other quarters. There is no case for a second independence referendum.”

The row comes as an explosive poll suggested the majority of Scots now supported independence. The survey, commissioned by former Tory Chairman, Lord Ashcroft also revealed that a third of Labour's voters would back independence.

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."

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.”

Ian Murray, Labour MP for Edinburgh South, said: “These are utterly irresponsible comments from John McDonnell that betray our party’s values.

“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.”

MSPs voted 69-59 two years ago for a Section 30 order, but Theresa May refused to grant one, saying now was not the time for another vote.

A Scottish Labour spokersperson said: "John McDonnell was clearly not advocating a second independence referendum. He made clear the huge benefit a UK Labour government will bring for the people of Scotland.

“Labour stands for an end to the status quo in the UK: economically, politically and constitutionally. The real change we need to see in society is an end to austerity and investment in our people, our communities and our public services.”

Responding to John McDonnell’s comments on independence at the Edinburgh fringe, Scottish LibDem leader Willie Rennie said: “These comments are astonishingly irresponsible and not in interests of Scotland or the UK.

“It’s bad enough with Boris Johnson bungling on Brexit and independence but to have the Labour Party’s Chancellor piling in makes it a whole lot worse.

“It’s clear only the Liberal Democrats are robustly standing up for Scotland’s place in the UK and the EU.”