NICOLA Sturgeon spent almost £140,000 of public money on a doomed intervention in the UK Supreme Court hearing on Article 50, it has emerged.

The Scottish Government slipped out the figure last night in a written parliamentary answer.

It showed the total cost was £136,418, of which £128,877 was external legal fees.

Another £6,231 was spent on travel, accommodation and food for government officials in London, £800 on the fee to intervene in the case, and £510 on a room and catering at court.

The central issue in the December hearing was whether Westminster’s approval was required before the UK Government could trigger the EU withdrawal process.

However the Scottish, Welsh and Northern Ireland governments also intervened.

Scotland’s top law officer, the Lord Advocate James Wolffe QC, argued the triggering of Article 50 should be the subject of a vote by MSPs in Holyrood.

He said that because Brexit would change the powers of the Scottish Government and Scottish Parliament it was covered by the Sewel Convention, which says Westminster should not normally legislate in devolved areas with Holyrood’s consent.

However the judges flatly rejected his argument, affirming that the Sewel Convention was merely a political agreement, not statute, and therefore outside the remit of the court.

Mr Wolffe appeared to accept as much during the case, when Lord Hodge asked if he recognised that the court could not adjudicate on a convention or what was “normal” under it.

The Lord Advocate replied: “I accept all of that, my Lord.”

Lord Wilson said many on the bench were “struggling” to see how the convention was relevant to the hearing.

Ms Sturgeon said the ruling MSPs were not entitled to a vote exposed “the very foundations of the devolution settlement... to be worthless”.

The court ultimately ruled Westminster had to approve Article 50, leading to the recent passing of the EU Withdrawal Act.

Scottish Tory constitution spokesman Adam Tomkins said: “Nicola Sturgeon's attempt to stir up grievance on what was always a doomed legal bid has landed taxpayers with a £136,000 bill.

“This is a complete waste of public funds and the SNP Government should apologise immediately to the teachers, doctors and public sector workers neglected while Nationalists spent valuable taxpayers' money on their unwanted and unjustified separation agenda.”

Releasing the figures, SNP Brexit minister Michael Russell said the Lord Advocate had intervened “given the significance of the case for the UK’s constitutional arrangements, and the effect on devolved competence of notification under Article 50”.