Hague: Labour government propped up by the SNP would be dangerous and unstable

He called on voters to think about the potential pitfalls before they cast their vote on May 7.

In comments that will infuriate Labour the former Foreign Secretary also said that the SNP would encourage the party into a "leftward drift".

Speaking to journalists at Westminster, he said: "It would be a dangerous situation for any government to be dependent on the votes of the SNP - and that will be a factor people will have to think about in the General Election."

Later he added: "The dangers are of an unstable coalition or a minority government, which is dangerous in any circumstances, and of a very leftward drift.

"We are already faced with a Labour with little understanding of business and enterprise and I think there would a danger of the SNP pushing the Labour party even further in that direction with damaging consequences for the whole UK economy."

A spokesman for Nicola Sturgeon said that his comments showed that the Conservatives were "running scared" of the SNP's surge in the opinion polls.

Labour said that the real risk to Scotland was another five years of a Tory government at Westminster.

Mr Hague, who is standing down at the General Election, also defended his plans to restrict the voting rights of Scottish MPs, saying that the "issue of accountability and democracy in England has to be addressed and I think it is impossible to avoid".

The Tories want to introduce a system of so-called 'English votes for English laws".

But the SNP and Labour have questioned the definitions of 'English-only' legislation.

Ms Sturgeon has announced that her party will vote on issues including on health and education in England after May, arguing they have significant knock-on effects in Scotland.

A spokesperson for First Minister said: "William Hague's comments show the Tories are running scared of the SNP surge and of the prospect of the SNP's strength keeping them out of office after May."

He added that only the SNP was "capable of standing up for Scotland"at Westminster, including on questons like Scotland's place in Europe, which the Tories were putting "in grave danger".

Shadow Scottish Secretary Margaret Curran said: "The real risk to Scotland is five more years of a Tory government that would take public spending back to the 1930s, before we had the NHS.

"Only Labour is big enough and strong enough across the UK to kick the Tories out.

"Every vote for the SNP risks another Tory Government."

Mr Hague also said that he wished he had done more to increase the number of women and ethnic minority Tory candidates while in charge of the party.

But he declined to say whether or not he thought that the UK should continue to meet the Nato target of spending 2 per cent of GDP on defence during the next parliament.

He said he "strongly supported the fact we had met the 2 per cent in this parliament and we had encouraged other countries to do so".

"It's important that we have done that over recent years... as for future commitments that is for manifestos or future commitments," he said.

"The important thing is we retain strong and effective defences."