Ruth Davidson is understood to be on the verge of quitting as leader of the Conservatives in Scotland.

In what would be a major blow for prime minister Boris Johnson, reports suggest Ms Davidson will announce her departure in a statement on Thursday.

The 40-year-old has turned round the Tories’ fortunes north of the border since taking the helm eight years ago, making the Conservatives the second largest party at Holyrood. Her success has led to her being tipped as a possible future leader of the party nationally, though she has said she does not want the job.

But she has clashed with Johnson over her refusal to support a no-deal Brexit, and backed rival Jeremy Hunt in this year’s leadership contest.

News of her expected resignation came as the PM announced plans to suspend parliament for more than a month in the run-up to the Brexit deadline of 31 October, in what critics have described as a “coup” to make no-deal possible.

But Tory insiders said she was expected to make clear in her statement that her resignation was not linked to Mr Johnson's elevation or to his decision to "prorogue" the Commons.

Scottish first minister Nicola Sturgeon has urged Ms Davidson to join cross-party efforts to prevent the UK crashing out of the EU on Halloween without a deal.

The Scottish National Party leader tweeted: "Given her past statements opposing a no-deal Brexit, it would be good to have confirmation from Ruth Davidson today that all Scots Tory MPs will back the cross-party effort next week to stop it - and that they will also oppose Boris Johnson’s attempt to shut down parliament.”

There was no response from Ms Davidson’s office to repeated requests for comment, while Conservative central office in London was unable to confirm or deny reports of her planned resignation.

Scottish Labour MP Ian Murray, a supporter of the Best for Britain campaign for a second referendum, said: Best for Britain supporter Ian Murray MP said: “Ruth Davidson is a formidable politician and her departure will be deeply felt by her party.

“She campaigned tirelessly for a Remain vote in the EU referendum, but the Tories under Boris Johnson have become a hard Brexit party, so it is not surprising that it has come to this.