THERESA May has put her civil servants on standby in the expectation that Nicola Sturgeon will call a new independence referendum when Article 50 is triggered next month.

Downing Street is said to be preparing for the possibility of the First Minister making the announcement as the formal process to take the UK out of the European Union begins, according to a report.

Senior UK Government insiders have said there is serious concern in Whitehall about the prospect, given that civil servants are already under pressure from the Brexit vote and are also concerned about the possible collapse of power-sharing at Stormont.

“It is possible that we will have to face Nicola Sturgeon calling a second referendum, have to bring in direct rule in Northern Ireland and trigger Article 50 all at the same time,” one insider told The Times.

There has to be agreement between the UK and Scottish Governments before a new referendum can be held.

The 2014 vote was based on the Edinburgh Agreement, signed by then Prime Minister David Cameron and then First Minister Alex Salmond. This allowed both governments to bring forward a Section 30 order, giving the referendum a legal base.

Both sides agreed that the referendum should take place before the end of 2014 and “meet the highest standards of fairness, transparency and propriety, informed by consultation and independent expert advice”.

May, who heads to Glasgow this week to address the Scottish Conservatives conference, could reject the First Minister’s demand for a new vote, but is aware that doing so is likely to strengthen pro-independence feeling.

On the other hand, according to the report, if she agrees to a new referendum, she has been told she could risk the break-up the UK on a “coin toss”. A poll taken earlier this month showed support for independence had increased to 49 per cent.

The Prime Minister has promised to trigger Article 50 by the end of March and expects to be able to stick to the timetable, despite ongoing parliamentary wrangling over the process.

The news, which reflected previous reports earlier this month that both UK and Scottish Government civil servants were preparing for a new referendum, came as May urged voters in Scotland to use the forthcoming council elections to make clear to Sturgeon that another independence referendum is not wanted.

Writing in the current issue of Holyrood magazine, the Prime Minister said her party would be “looking forward to the local elections in May, when voters across Scotland will have the chance to send a clear message to the SNP that they do not want a second independence referendum, by voting Scottish Conservative and Unionist”.

Ever since the UK voted to leave the EU but Scotland voted to remain in June last year, there has been speculation that the Scottish Government will seek to hold another independence referendum.

Sturgeon has warned that May’s plans for a hard Brexit, taking the UK out of the single market, “undoubtedly” made that a more likely prospect.

An SNP spokesman said: “There is already a cast-iron democratic mandate for an independence referendum – that was delivered in last year’s Holyrood election, however much the Tories might try to deny it.

“That mandate also stems from the EU referendum, which saw Scotland vote by a 24-point margin to stay in Europe – and Theresa May’s reckless pursuit of an economically ruinous hard Brexit will only strengthen opinion in Scotland against leaving Europe.

He added: “The Prime Minister couldn’t be more wrong to suggest there is considerable common ground between her Government and the Scottish Government on Brexit – her party is hell-bent on taking us out of the world’s biggest single market, with all the economic damage that would cause, while we are intent on protecting Scotland’s vital national interests.”

Downing Street said May remained opposed to a second referendum, although a spokesman refused to be drawn on whether she would block a new vote if Sturgeon decided to call one.

“I’m not getting into hypotheticals,” the spokesman said.

He continued: “There was a vote in 2014. The people of Scotland made a decision then to remain in the Union. All the evidence around would suggest that Scotland doesn’t want another referendum.

“It was a fair, legal and decisive result. Both sides agreed they would abide by the result.”

Labour MP Ian Murray said: “The Tories have consistently put the Union at risk with their reckless actions in government, including the drive for a hard Brexit and the decision to introduce English Votes for English Laws. The Union is not safe in Theresa May’s hands.”