BORIS Johnson becoming Prime Minister would be a “disaster for Scotland and the Conservatives,” senior Tory sources have said, warning it would “gift-wrap independence” for Nicola Sturgeon.

The SNP leadership insisted having a “nutter” in Downing St from the Conservative Brexiteer faction should not just worry the people of Scotland but everyone across the UK.

As the Conservative Party prepares for a forthcoming leadership election, following Theresa May’s announcement earlier this week, Scottish Tory sources expressed deep alarm about the prospect of the former Foreign Secretary winning the contest.

One Conservative MP told The Herald: “He is disliked intensely in Scotland and would gift-wrap independence for Nicola Sturgeon.”

Another senior insider said: “If Boris becomes PM, it would be a disaster for Scotland and the Conservatives.”

A third noted: “Boris is not seen as an asset for the party in Scotland. He does not play well in Scotland; he does not set the heather on fire for all the doubts people have expressed about his suitability for high office.”

Allies of Ruth Davidson, who is hoping to supplant the SNP leader as First Minister at the Holyrood election in 2021, fear a Johnson premiership would be fatal to her chances of success.

The Scottish Conservative leader, who was a leading Remainer during the 2016 referendum campaign, has clashed directly and indirectly with Mr Johnson in recent times.

During the EU referendum campaign, she claimed the London MP and other prominent Leavers had “lied” over the Brexit campaign’s claims and called for a “period of silence” from Tory colleagues after Mr Johnson branded the PM’s Brexit plan “deranged”.

Last October, Scottish Conservatives, concerned about the prospect of Mr Johnson entering No 10, announced the establishment of “Operation Arse,” a campaign to stop him becoming PM if he ever launched an official bid. One senior Tory at the time noted: “We called it that so we’d all be clear who we were talking about.”

Last night a party insider told The Herald: “The moment has arrived for Operation Arse to swing into life.”

It is also believed David Mundell would not expect to be part of a Cabinet led by the right-winger.

In light of Mrs May’s decision to stand down, the Scottish Secretary said it was important her successor was as “absolutely committed” to “preserving the UK” as she was.

But one party insider noted how during the lengthy Scottish independence campaign he could not recall Mr Johnson - who is portrayed as a staunch Unionist - ever venturing to Scotland to save the Union.

While Scots Tories believe a Johnson premiership is privately desired by SNP chiefs because they believe it would boost the independence cause, the Nationalist leadership made clear it was aghast at the prospect of the former Cabinet Minister seizing power.

Asked if Mrs May’s successor could be worse from the SNP’s perspective, Ian Blackford, the party’s leader at Westminster, declared: “Oh, God almighty, absolutely.

“The Tory Party is becoming increasingly Brexiteer; we all know what is happening with its membership and everything else…God forbid, someone like Boris Johnson[takes over].”

The Highland MP, referring to the future part of the Brexit process concerning trade and the longer term relationship with the EU, noted: “If you’re giving the levers of this to someone who is one of the nutters from the ERG or someone at least close to the ERG, then goodness knows where we are going to end up. There is a very real worry as to the impact of Theresa May’s departure.”

The Nationalist leader added: “She is an absolutely appalling prime minister. The way she has handled the last few days has been absolutely disgraceful but the thought of the keys to No 10 being in the hands of a Brexiteer is something that should worry not just the people of Scotland but everybody else in the UK as well.”

Following yesterday’s Government defeat on the Withdrawal Agreement, it is possible any Tory leadership election could begin in late April after the possibility of the EU granting a lengthy extension.

Among those who are expected to be in the running alongside Mr Johnson are: Jeremy Hunt, the Foreign Secretary; Sajid Javid, the Home Secretary; Michael Gove, the Environment Secretary; Matt Hancock, the Health Secretary; and Amber Rudd, the Work and Pensions Secretary. It is thought if the London MP can get into the run-off between the final two candidates, then, given his popularity among the grassroots in England, he could win.

Mr Johnson was approached for a response but none was forthcoming.