THERESA May believes Nicola Sturgeon does not have a mandate to hold a second Scottish independence referendum, No 10 has said.

After becoming Prime Minister, the Conservative leader on a visit to Edinburgh in July said: “As far as I’m concerned, the Scottish people have had their vote, they voted in 2014 and a very clear message came through. Both the United Kingdom and the Scottish Government said they would abide by that.”

Later, asked if the UK Government would seek to block the SNP Government holding another independence vote, Mrs May stressed it was not a question of whether it could hold a second referendum but whether it should. Scottish secretary David Mundell has called on the First Minister to rule out a second poll, saying it was creating a great deal of business uncertainty following the Brexit vote.

However, the First Minister has maintained that it is “highly likely” that there will be a second independence vote given the context of Brexit and the fact that 62 per cent of Scots voted to Remain in the European Union.

Tomorrow, Ms Sturgeon is expected to set out further her thoughts on Brexit and another poll on Scotland’s future when she addresses the Institute of Director’s annual convention at London’s Royal Albert Hall.

The SNP’s 2016 Scottish parliamentary election manifesto stated: “We believe the Scottish Parliament should have the right to hold another referendum if there is clear and sustained evidence that independence has become the preferred option of a majority of the Scottish people, or if there is a significant and material change in the circumstances that prevailed in 2014 such as Scotland being taken out of the EU against our will.”

In the Holyrood poll in May, the SNP lost its overall majority but remains the largest party with 63 seats.

Last week, at a charity lunch, Ms Sturgeon defended her stance of keeping a second independence vote on the table, saying: "If we don't retain the option, we would be accepting that no matter how damaging to our economy and society Westminster decisions turn out to be, we would be powerless to choose a better future. I don't think that would be sensible or an acceptable position to place ourselves in."

Asked if the Prime Minister regarded the FM’s position on the possibility of holding another independence referendum as a serious option or an idle threat, her deputy spokesman replied: “The Government does not believe there is a mandate for a second referendum.”