Cabinet minister Vince Cable has become the second Lib Dem to raise the prospect of the break-up of the Conservative-Liberal Democrat coalition before the next general election, by talking of the need for the "disengagement" of the two parties.

The Lib Dem Business Secretary said the governing parties would need time to "establish their own separate platforms and identity" before they went to the country again in 2015.

His comments raise crucial questions about the nature of the Government towards the end of the current parliament. The coalition has legislated for fixed-term five-year parliaments, with the next general election due in May 2015.

Cable has become the second Lib Dem to talk openly about the coalition's prospects for survival, after the party's president Tim Farron used a HuffPost interview to reveal there were "blueprints for disengagement" last week.

Farron told us: "We have some blueprints, some models. They are basically Scotland and some of our colleagues over the water in Europe where coalition is more usual. The first time it happens will always be the hardest, all of this is new to everybody."

Asked whether the Lib Dems would break away "just short of the election to give itself a bit more space to establish an independent platform", Dr Cable told BBC Radio Five Live: "Everybody involved knows that before the next general election, the two parties will have to establish their own separate platforms and identity.

"But how that disengagement takes place, over what time period, is very much an issue for the future, certainly not something we're talking about at the moment."

The Lib Dems would be "competing as a separate party with a separate manifesto and I am sure the Tories think exactly the same way", he said.

Dr Cable notoriously told undercover reporters from The Daily Telegraph in 2010 that he had the "nuclear option" available to him of bringing down the coalition by quitting the Cabinet.

But he told Five Live that he was now "committed to staying the course", adding: "I was speaking off the cuff and in rather an emotional context. I wasn't giving a cool analysis of political situation.

"My position is I am working very effectively with my colleagues in the coalition. We have got a massive, massive economic problem to deal with - partly problems we have inherited of a collapsed financial system and partly a difficult international environment."

Asked whether David Cameron agreed with Dr Cable's assessment that the coalition parties may have to disengage ahead of the 2015 election, a Downing Street spokeswoman said: "The key word in that statement is 'may'."

The spokeswoman told a regular media briefing in Westminster: "He was speculating to a hypothetical question.

"Clearly, we have a coalition Government with a challenging programme which it is focused on delivering."