Almost two-thirds of Tory members want Brexit to take place even if it means Scotland gaining independence, according to a new poll.

The YouGov survey, which has been described as "an utter disaster" for Ruth Davidson, found 63% of party members would be happy to see Scotland leave the UK if Brexit took place.

Researchers also found 61% of party members would not care if Brexit caused "significant damage" to the UK economy, while almost half (46%) said they would be happy to see the Brexit Party's Nigel Farage as their new leader.

SNP depute leader Keith Brown said the results show Scottish Tory leader Ruth Davidson has little authority within her party.

"The Tory Party has clearly gone off the deep end - with their Brexit obsession pushing the party further towards the extremes," he said.

"Tory members are so determined to deliver a damaging Brexit they are happy to watch our economy collapse and open the door of number 10 for Nigel Farage to take control of the UK.

"And far from prioritising the union, it's clear Scotland means so little to the members of the Conservative and Unionist Party that two-thirds are happy for Scotland to become independent if it secures Brexit."

He added: ""With this poll suggesting that almost a quarter of Tory members in Scotland would prefer to deliver Brexit for their membership down south even if it means an end to the union, it's becoming clearer that Ruth Davidson has little authority in her party in Scotland.

"This poll is an utter disaster for her and shows that her authority is seeping away at an incredible rate, leaving her increasingly isolated."

Nicola Sturgeon, who will deliver a speech on Tuesday night to mark the 20th anniversary of the founding of the Scottish parliament, said the Tories could cause more damage to Scotland in the next 18 weeks than they did in the 18 years when Margaret Thatcher and John Major were in power.

"Immense damage to Scottish communities was caused by an out of touch Conservative Party that governed, unelected in Scotland, for 18 years," the First Minister will say.

"But now I fear a similarly out of touch Tory Party, led by an even more reckless leader, could cause as much damage as Mrs Thatcher and John Major did.

"But while they took 18 years, he, whoever it is, could do as much - or more - damage in just 18 weeks.

"Because by the end of October, Scotland could be heading for a no-deal Brexit."

A spokesman for the Scottish Tories said: "Conservative members need to remember ours is a party of the whole UK.

"It's in the name. If Scotland becomes independent, there is no UK.

"No matter how badly people want Brexit, no Conservative and Unionist member should be prepared to turn their back on the UK."