Ruth Davidson could resign as leader over Theresa May's Brexit strategy

Ruth Davidson could resign as the leader of the Scottish Tories in a bitter row over Theresa May's Brexit strategy, it has emerged.

Scottish Secretary David Mundell has also warned the Prime Minister that he could quit the Cabinet if she signs up to any deal which increases customs checks between Northern Ireland and the rest of the UK.

Both of them believe that any such arrangements could bolster the case for Scottish independence as the UK government would be agreeing to treat Northern Ireland differently from the rest of the country.

Holyrood’s sister site, PoliticsHome, has learned that Davidson - who has recently gone on maternity leave ahead of the birth of her first child - and Mundell have written to the Prime Minister setting out their concerns.

May is already facing the threat of resignations from Cabinet Brexiteers such as Andrea Leadsom and Esther McVey, while former Brexit Secretary David Davis has today urged other ministers to revolt.

A Scottish Tory insider acknowledged that the Prime Minster was "walking the fine line of recognising Northern Ireland's unique position and landing a deal", but insisted that Davidson and Mr Mundell's walkout threat was real.

They said: "Not putting a new border down the Irish Sea has been the Scottish party's red line from the start.

"If anyone thinks Ruth and David care more about the Tory party than the United Kingdom, they are kidding themselves. They are not the threatening or flouncing types, but this is an article of faith."

May is facing mounting pressure ahead of a crunch EU Council summit in Brussels later this week.

Before then, she will make a final attempt to sell her plans at a Cabinet meeting on Tuesday. Failure to do so could spark a wave of resignations which could end up sweeping her from office.