A victory for Jeremy Corbyn would be a boost to the SNP’s bid for Scottish independence, Ruth Davidson, the Scottish Conservative leader, has warned.

She said, faced with the prospect of the left-winger winning the Labour leadership contest: "The Conservative in me is delighted; the Unionist in me is crying into my beer."

After Mr Corbyn described himself as a “Socialist not a Unionist” and revealed that he had not campaigned once to save the United Kingdom during last year’s referendum campaign, Ms Davidson said that if he won the race for the Labour crown, then he would “run up the white flag on our Union”.

Ahead of a keynote economic speech in London, the MSP said: “The more the politics of the rest of the UK looks like a foreign country than Scotland, the easier it is for the SNP to try and paint that Englishness and otherness they do so effectively and disgracefully.

"Having a neo-Marxist in a Breton cap talking about 1970s politics just takes us further away from where Scotland is."

Ms Davidson said, among the Labour candidates, she most admired the outsider Liz Kendall’s “directness, decisiveness and tenacity”, admitting also: “She would be the one I would fear most,” adding with a laugh: “Such a shame she is going to come fourth.”

The party leader described Yvette Cooper’s campaign as lacklustre and bereft of any dynamic policy offer.

“She had a real come-through-the-middle strategy of being everybody’s second choice…If you are going to be a leadership contender, you have to be prepared to lead…Her campaign has been about not wanting to be everybody’s last choice rather than being anybody’s first choice.”

Ms Davidson said if a female candidate were to win the Labour leadership, then the atmosphere in the Commons chamber would be very different.

“It’s much easier for a male leader in a very combative chamber like the Commons to take on another male and attack them; you can’t do that with women. You look either feart or weak if they beat you. The dynamics would change hugely if there was a female leader,” she added.