Former defence minister Sir Nick Harvey said any negotiations after this May’s vote could take up to a month, unlike the 2010 coalition deal which was thrashed out in just five days.

Mr Harvey said that as the incumbent Prime Minister, David Cameron should remain in Downing Street until a deal was struck.

But he suggested that if the Conservative leader wanted to leave then Nick Clegg could fill the role - assuming the deputy prime minister keeps his seat.

“I personally think that they should take at least a month,” he told the Huffington Post.
“And I think that what you need during the course of that month is some sort of interim government. Where you’ve got a prime minister and home secretary and a chancellor. And maybe a deputy prime minister. I don’t think it is right to appoint a government of 121 members until such time as you have a deal. If the deal is going to take a month, you could just appoint a government of eight or ten ministers.”

He added: “If it was a Lib-Lab discussion going on, Cameron ought to remain in office.
“Failing that of course, Nick Clegg is the deputy prime minister. There is no reason why he couldn’t act up for a few weeks.”