DOWNING Street has insisted that the constitutional debate in Scotland is 'settled' following remarks by the Scottish Secretary.

Alister Jack, the Secretary of State for Scotland, suggested this morning that another vote could be held in "25 to 40" years, citing the infamous "once in a generation" claim.

When asked about his remarks, a No.10 spokesman said the Prime Minister had been "clear" that the issue of independence was "settled".

He said: "The PM has said on countless occasions that the issue of independence was settled when the Scottish people voted decisively to remain part of the UK.

"It was billed at the time as a once in a generation vote and the Prime Minister has been clear that he believes that must be respected."

Asked if the PM would agree that a "generation" would be between 25 and 40 years, the spokesman said: "The fact is that people voted to keep our United Kingdom together. It was billed at the time as a once in a generation vote."

When asked if Mr Jack was speaking on behalf of the UK Government when he made the remarks, the spokesman said simply the Prime Minister's view was "clear".

It comes after a 12th poll in a row, published yesterday by Survation, found that a majority of Scots now support independence. 

The survey found that 54 per cent of people were in favour of independence. 

Read more: Nicola Sturgeon & Ian Blackford hit back after UK ministers say 'no for a generation'

The SNP have hit back at Mr Jack's comments this morning, arguing that they are straight from the "Trump playbook".

Mhairi Black, the SNP’s Shadow Scotland Secretary said: "The Tories' attempts to employ tactics straight out of the Trump playbook and deny the people of Scotland the right to choose their own future is completely unsustainable, undemocratic and doomed to fail.

"Just as Donald Trump will have to accept the will of the people if the US election goes against him, so will Boris Johnson have to accept the will of the people of Scotland in next year’s Holyrood election. 

"With poll after poll concluding that independence is now becoming the settled will of the majority of people in Scotland, it’s telling that Alister Jack is shamelessly shifting the goalposts given his previous contradictory comments over a second referendum - the Tories are rattled. 

"Scotland's interests and democratic decisions have been repeatedly ignored and discarded by a detached and broken Westminster system – it is little wonder that support for independence is growing.

"The SNP will continue to make the case for a progressive, fair and inclusive independent Scotland that will be an equal partner with our friends in the EU.

"Scotland’s future should be in Scotland’s hands, not Boris Johnson’s reckless Tory government - which Scotland did not vote for."

In September, a fiery exchange took place between the Prime Minister and SNP MP Angus MacNeil at a committee hearing in Westminster.

Mr MacNeil challenged Mr Johnson over whether he would grant the Scottish Government a section 30 order, which would give it the power to hold a second referendum.

However the Prime Minister said that based on his "understanding of human biology", a generation had not passed since 2014.