The Shadow Business Secretary claimed it would be "catastrophic" if there was no outright majority as the country tried to emerge from the economic crisis.

He said the Tories were "probably going to win", but, nevertheless, the party still had to "work like mad" to ensure leader David Cameron could achieve a majority.

Speaking at a lunch at Westminster, Mr Clarke said: "I do think that, in the middle of an acute national crisis, a hung parliament would be one of the biggest disasters we could suffer."

He said it would take "a generation" for the British public to become accustomed to dealing with coalitions in power and he warned: "That would be a bigger danger than a Labour victory."

In a candid performance, Mr Clarke also revealed that the Tories would move swiftly to introduce legislation to allow a private company to take a stake in the Royal Mail.

And he said the Bank of England's bid to revive the economy through quantitative easing would eventually fuel inflation but he did not expect interest rates to rise for "12 to 18 months".

Mr Clarke also spoke of his respect for his opposite number Lord Mandelson, but dismissed suggestions that the Business Secretary should be able to answer MPs' questions from the Bar of the Commons.

"I'm rather against that, being an old-fashioned constitutionalist," he said.