Ruth Davidson made the claim when giving her backing to the Prime Minister’s after she said she supported plans for the Prime Minister to stay in post after she said she planned to lead the party in a 2022 general election.
The Scottish Tory leader also backed the decision to hold the snap poll in June, claiming it stopped the SNP moving towards another referendum on Scottish independence.
“Theresa May might have lost her majority but by God she saved the Union,” she told The Times.
Davidson also called for “serious people” to take charge of Brexit as the Conservative Party gears up for its conference.
The Scottish Tory leader told The Times that she believes “over-optimism” about the the future of Britain outside the EU “sells people short”.
She reportedly denied that the comment is directed at Foreign Secretary Boris Johnson, who recently laid out his own path for a “glorious” future outside the bloc.
In an interview with the newspaper, Ms Davidson took aim at those setting out what she sees as an unrealistic prospectus.
She said: “I think optimism, positivity is good. I think overoptimism and not recognising that there are practical realities that have to be faced, that have to be worked through and that complexity is not something you just skip over, that you actually have to work through, I think sells people short.”
Earlier this month, Mr Johnson set out a detailed vision for Britain’s exit from the European Union that revived the claim Brexit could boost NHS coffers by £350 million a week.
In an article for the Daily Telegraph, he insisted Brexit will allow the UK to “be the greatest country on earth’’ and “our destiny will be in our own hands’’.
Questioned about Mr Johnson’s message, Ms Davidson told The Times: “I don’t take issue with optimism. I am quite often accused of having a kind-of, sort-of have-a-go element about myself as well.
“But there is the idea that this is quite hard and it needs serious people to do a lot of legwork and scan the detail to make sure we do get to a place where it will all be OK. It doesn’t just happen by accident, it requires a lot of hard work and it requires application.”
She also said the £350 million a week figure “wasn’t a figure I recognised”.
Earlier this month, fears that Brexit could deliver a blow to the economy which the country does not recover from were raised by the Scottish Tory leader.
The remain campaigner conceded Brexit ‘’is going to happen’’ but said she was concerned there would be a short-term economic hit and “we don’t bounce back from it”.
Recent polling by YouGov put the Foreign Secretary as the top choice to take over as party leader from Theresa May, with support from 23% of party members. He was followed by Ms Davidson on 19%.
Despite the backing of 19% of activists in the poll, Ms Davidson has ruled out leaving Holyrood before the next Scottish Parliament elections in 2021, the newspaper said.
The Conservative Party conference takes place in Manchester from Sunday until Wednesday.