Conservatives shouldn't be welcoming the prospect of a lot of SNP MPs being elected at the expense of Labour in Scotland, Ruth Davidson has said.

The Scottish Conservative leader's comments follow a warning from senior Tory peer Lord Forsyth that building up the SNP to undermine support for Labour in England could ultimately damage the Union.

''We've had the dilemma for Conservatives, which is they want to be the largest party at Westminster and therefore some see the fact that the nationalists are going to take seats in Scotland will be helpful,'' he told the Guardian. ''But that is a short-term and dangerous view which threatens the integrity of our country.''

His intervention came as Sir John Major endorsed warnings by David Cameron about the dangers of a post-election deal between Labour and the SNP.

Speaking on BBC Radio Scotland's Good Morning Scotland programme, Ms Davidson said: "What the Prime Minister is saying, what I have been saying for months and months, is that doing some sort of dodgy deal between the Labour Party and the SNP is bringing the SNP closer to breaking up Britain.

"Every single thing that the SNP does, whether that's writing white papers full of dodgy facts and figures full of fantasy economics, making up EU legal advice, everything they do is about bringing Scotland closer to independence.

"Putting Ed Miliband in Number 10 is about bringing Scotland closer to independence for them too."

She added: "One of the things I do agree with Lord Forsyth about is that the Tory party shouldn't be welcoming the idea that there is going to be a lot of SNP MPs at Labour's expense.

"I think the problem is that while the Conservative Government has responsibility for many things, 10 years of decline and implosion of the Labour Party in Scotland is not one of them."

She added: "I think Lord Forsyth has fallen into a bit of a nationalist trap by framing this as a Scotland versus England thing, and it is not, because unionists across the whole of the UK are concerned and frightened about the sort of concessions that the SNP being in charge of a weak Labour government could bring."