Theresa May has rejected the SNP’s claim that Brexit justifies staging another independence referendum as she was warned that her “days as Prime Minister of a United Kingdom are numbered" if Scotland’s remain vote is ignored.

The Prime Minister’s official spokesman said Nicola Sturgeon should stick to her pledge that the 2014 referendum was a “once-in-a-generation” vote and urged her to respect Scots’ decision.

But Angus Robertson, the SNP’s newly-elected deputy leader, told the party conference in Glasgow that “Remain means Remain” for Scotland and warned Mrs May that ignoring this would mean the end of the UK.

Ms Sturgeon argued it was “inconceivable” that Mrs May could prevent a second referendum being staged despite the 2014 precedent showing that Westminster’s consent would be required.

The First Minister argued that Scotland is in a situation it did not choose in the EU referendum and she could not see how the UK Government could justify refusing another vote on leaving the UK.

The row broke out the day after Ms Sturgeon disclosed she will publish a draft referendum bill for public consultation next week. However, constitutional affairs are reserved to Westminster.

Mrs May’s spokesman said: "There was a referendum in 2014 that addressed this issue that was legal and fair. The result was decisive and both parties agreed at the time to respect it.