Ruth Davidson faces a challenge for her Holyrood seat from one of the SNP’s biggest hitters, it has been reported.

Angus Robertson, the SNP’s former Westminster leader, is claimed to be considering running in Edinburgh Central, which the Scottish Tory leader won in 2016.

Mr Robertson was the Nationalists’ deputy leader until standing down last year. He lost his Moray constituency to Scottish Tory MP Douglas Ross in 2017.

Considered one the SNP’s heavyweights, he now runs the Progress Scotland research group, aimed at preparing the case for independence.

Read more: Tom Gordon: PM’s Brexit chaos overshadows Ruth Davidson’s return

He told the Sunday Times, which reported the latest claims: “While it is an honour to be linked by others to the constituency, the nomination process has not even started.

“I am totally focused on my work with my new venture Progress Scotland, and to the challenges of impending parenthood.”

It is understood First Minister Nicola Sturgeon wants Mr Robertson to return to frontline politics.

The move would see Edinburgh Central become one of the key battlegrounds in the 2021 Holyrood elections, with rumours that former Scottish Labour leader Kezia Dugdale is also eyeing it up.

A Scottish Tory source said: “Earlier this year the MEP Alyn Smith was being lined up to take on Ruth. Now apparently it’s Angus Robertson.

“Who next? On behalf of the great city of Edinburgh, the Scottish Conservatives welcome them all.”

It came as a Scottish Tory source told the Sunday National that members are considering splitting from the UK party if Boris Johnson becomes Prime Minister.

Read more: Ruth Davidson 'likely' to be Scotland's next first minister

The source said: “There have been various murmurings around the formation of a separate Scottish party in the past.

“Indeed, there have been suggestions coming from sources close to Ruth that it might be something she might favour.

“Certainly, if Boris became Prime Minister there would be a lot of discussions in the Scottish party about what it would mean for us.

I wouldn’t rule anything out.”

Tory sources previously insisted Mr Johnson getting into power would be a “disaster for Scotland and the Conservatives”.

One MP said he is “disliked intensely in Scotland”.