Lord Heseltine said David Cameron had done a fantastic job
The next general election is "very likely" to produce a hung parliament, former deputy prime minister Lord Heseltine has said.
This was because to take overall control, the Conservatives needed the biggest electoral swing, "with two exceptions, since the war", he said.
Speaking on the BBC's Straight Talk with Andrew Neil, Lord Heseltine ruled out a return to government.
David Cameron "does not need 77-year-olds in his government", he said.
Lord Heseltine would be that age by the time the next election is held.
"We do not have the physical stamina to sit up all night reading those interminable papers, arriving for breakfast meetings or whatever it may be, six days a week, or five-and-a-half days a week," he said.
"Any advice we can give is free and available and welcome... but you mustn't think in terms of recruiting people like me."
He said that Mr Cameron "had done a fantastic job".
"But in order to get an overall majority, David has got to have the biggest swing, with two exceptions, since the war.
"I think David is doing a very good job, I think that the odds on him winning are significant, but the overall majority is a mountain to climb and I think he's been absolutely right in making this point clear.
"I think it's very unlikely we'll see a Labour government, that I do believe.
"Then you come to another problem - there are not many parties... that will form any sort of relationship with the Conservatives, so the Conservatives have got to win outright or be sufficiently the largest party that there isn't a coalition against them and they face the House of Commons, which of course will mean a relatively short Parliament."
Lord Heseltine also said he agreed with the original mission in Afghanistan but he was at a loss to "understand the mission creep where we're now trying to change the whole political cultural ethos of a country".
"And if you're going to choose a country to do it, probably the one you would not choose is Afghanistan."
He said the Afghan government "is corrupt, it is a patchwork quilt of deals done with people whose political integrity is not worth talking about".
"And there is the most effective guerrilla experience, 100 years in the making. So it is a nightmarish situation."
Lord Heseltine also said invading Iraq "was a terrible mistake".
He added: "I had no time for Saddam Hussein, but in terms of the stability of the Middle East, Saddam Hussein had been an important ally in Western interests in stability.
"If you overturned him, which is what we then did, there was going to be instability in a country which he had ruled with a rod of iron, often very unacceptable ways, but once you take him out then the consequences are to be seen on the streets of Baghdad."