In a new biography of the Scottish Conservative leader, Ms Davidson is said to have been “f***ing furious” when The Vow was put together by leaders in Westminster but her arguments were ignored.
The high-profile “Vow” by pro-union party leaders on the front page of the Daily Record two days before the referendum promised more powers for Holyrood if Scots voted No.
Andrew Liddle, Ms Davidson’s biographer, said the Scots Tory leader wanted more powers for Scotland but worried ‘The Vow’ would hand an advantage to the SNP after the vote.
In his book, Ruth Davidson and the Resurgence of the Scottish Tories, Mr Liddle writes: “Ruth was - in the words of one senior party insider - ‘f***king furious’ with Cameron over The Vow. While she had been consulted over the pledge, she was strongly opposed.
“The Scottish Tory leader - rightly- argued that The Vow would play right into the Nationalist narrative.
“SNP leaders would be able to suggest that they did not lose on the question of independence, but rather the vote was one about more powers.”
He adds: “One senior insider, who was with Ruth when the Vow was being discussed, said: ‘It was the only time she got angry during the campaign. She felt that this would allow the SNP narrative to get going again... “There were some interesting scenes in the Better Together office.”
A senior Conservative source confirmed the accuracy of the book’s claims to The Times, stating that Ms Davidson had always been robustly against The Vow.