RUTH Davidson has warned Boris Johnson directly about the fragile state of the Union after a poll found most Scots back independence.

The Scottish Conservative leader revealed she had flagged the findings to make sure Mr Johnson saw it and appreciated its significance.

“We sent all of the Scottish coverage of that poll down to the Prime Minister,” she said. The coverage included that in The Herald.

With Mr Johnson ramping up plans for a no-deal Brexit and an impasse over talks with Brussels, Ms Davidson also urged the PM to compromise with the EU, warning “millions” of struggling families could not afford the economic shock of no-deal.

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The survey by the Tory peer Lord Ashcroft found 52 per cent of decided Scots voters want to leave the UK, compared to 48 who want to stay.

Published on Monday and conducted after Mr Johnson entered Number 10, the poll also found 51% of Scots want a second referendum on independence by 2021. It was the first poll with a Yes majority in 30 months.

Giving her first reaction to it after being interviewed on the Edinburgh Fringe, Ms Davidson said: “Obviously it registers. That’s the first poll that showed them slightly ahead since 2017. We’ve had two years of polls showing the other side slightly ahead - that’s not made front page news.

“But we’re not complacent. We want to make sure the UK Government delivers for the whole of Scotland. The best way [is] to ensure the majority will of the country, which was to stay together, is honoured.”

Asked if the poll reinforced her warning to Mr Johnson about a no-deal Brexit endangering the Union, she said: “I think there’s going to be discussions going forward. The UK Government knows that. We sent all of the Scottish coverage of that poll down to the Prime Minister. I continue to support him in his goal of getting a deal for the country.”

Nicola Sturgeon has said she wants to hold Indyref2 in the second half of 2020 or sooner, but the Tory Government has so far refused to give Holyrood the power to let it happen.

However shadow chancellor John McDonnell yesterday said a future Labour government would not block a second referendum.

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“It will be for the Scottish Parliament and the Scottish people to decide that,” he said on the Fringe.

His comment flatly contradicted Scottish leader Richard Leonard, who said in March that a Labour government would not agree to Indyref2, even if Holyrood voted for it.

Ian Murray, the Labour MP for Edinburgh South, said Mr McDonnell’s “thoughtless rant” had been “utterly irresponsible” and an insult to the party’s Scottish MPs.

An SNP spokesperson said: “Ruth Davidson and the Tories are losing the argument over Scotland’s future and they’re panicking.

“It would be a democratic outrage for any Tory government to deny the people of Scotland the right to choose their own future, and this week’s poll shows such an anti-democratic position is completely unsustainable.”