SCOTTISH Tory leader Ruth Davidson opposed a cross-party call made during the height of the independence referendum to give the Scottish Parliament greater financial powers.

Davidson was sceptical about the so-called “Vow” as a campaigning tool and instead wanted her colleagues to “hold their effing nerve”, according to a BBC documentary.

However, a Tory source said Davidson fully supported the devolution of extra powers, but was against the “Vow” on strategic grounds.

The insider said she wanted to defeat independence in its own right and was worried that changing the message would provide the SNP with excuses.

Film-maker Paul Mitchell, whose previous work includes Inside Obama’s White House and The Death of Yugoslavia, is behind the “inside the indyref” documentary and the final episode will be broadcast this week.

Including exclusive interviews with the key participants on both sides, the episode focuses on the last stretch of the campaign where Yes overtook the No campaign.

One section focused on an opinion poll around two weeks from the vote which showed that independence was in the lead.

The snapshot triggered panic in Better Together - the cross-party group that backed Scotland staying in the UK - and resulted in a revamped strategy.

Until that point, the pro-UK parties had largely focused on the economic risks of independence, rather than co-ordinating an offer on enhanced powers for Holyrood.

Following talks between key players in Labour, the Conservatives and the Lib Dems after the opinion poll, a decision was made to guarantee extra financial powers in the event of a No vote.

Although the “Vow” was seen as a pivotal moment during the campaign, the documentary reveals Davidson’s misgivings about the approach.

Davidson described her view after a conversation with the then chancellor George Osborne, who was a key supporter of the shift: “The phrase I keep remember saying was ‘I wish people would just hold their effing nerve’.”

The Scottish Tory leader summarised the conversation: “We had a broad based discussion where frank views were exchanged.”

In another segment, Davidson revealed her frustration when Prime Minister’s Questions was cancelled and the three main Westminster leaders headed north to campaign:

“I was not a fan of the idea of the Prime Minister, and Ed Miliband, and Nick Clegg, all deciding at the last minute that they were going to chuck PMQs and dash to Scotland. Again, it was a gimmick. It really annoyed me.”

The comments on the “Vow” confirm a passage on the same subject in a biography of Davidson by journalist Andrew Liddle.

In his book, 'Ruth Davidson and the Resurgence of the Scottish Tories', Liddle wrote: “Ruth was — in the words of one senior party insider — ‘f***ing furious’ with Cameron over the Vow. While she had been consulted over the pledge, she was strongly opposed.”

SNP MSP George Adam said: "Ruth Davidson has let the cat out of the bag – the Tories opposed a Scottish Parliament from the very start and have stood against more powers for Scotland at every turn, so perhaps this shouldn't come as a surprise.

"Their recent power grab on Holyrood under the guise of Brexit is just the latest attempt to diminish the status of our national parliament - it's no wonder they're sliding in the polls.

"Ruth Davidson would be happy to see the Scottish Parliament downgraded to a mere parish council, with no control over how best we deliver vital public services and build a fairer society for all."