Man or a mouse? David Cameron is challenged by Tory MP Tim Yeo

DAVID Cameron’s leadership has come under attack from a leading Tory backbencher, who demanded the Prime Minister show whether he is “a man or a mouse”.

Tim Yeo, chairman of the energy and climate change select committee, challenged Mr Cameron over his opposition to building a third runway at Heathrow to boost growth as the recession continues.

The attack by Mr Yeo, a former minister who is not one of the usual right-wing rebels, came as an ICM poll revealed that almost half of voters believe that Chancellor George Osborne should be moved from his job.

And with Mr Cameron under pressure to reassert his authority in a reshuffle expected in the next few weeks, the poll showing 48 per cent believe Mr Osborne is not the right man to be Chancellor underlined a lack of public confidence in the government’s economic strategy.

Mr Yeo said an immediate decision to give the go-ahead to a third runway would show that his government has found its “sense of mission”.

He said: “The Prime Minister must ask himself whether he is man or mouse.

“Does he want to be another Harold Macmillan, presiding over a dignified slide towards insignificance? Or is there somewhere inside his heart – an organ that still remains impenetrable to most Britons – a trace of Thatcher, determined to reverse the direction of our ship?”

The challenge put the position of one of Mr Cameron’s protégés, Transport Secretary Justine Greening, in the spotlight, as the MP for Putney, Roehampton and Southfields in west London is a long-term opponent of a third runway.

She said yesterday that a decision to go ahead with it would “make it very difficult” for her to stay in the government.

Downing Street insisted the government will not back down on its opposition to a third runway for Heathrow.

“The coalition parties have made a pledge not to have a third runway and that is a pledge that we will keep,” a spokesman for the Prime Minister said.

“We don’t see the argument for a third runway.”

London mayor Boris Johnson, seen as the leading candidate to succeed Mr Cameron as Conservative leader, favours a new airport built in the Thames Estuary – dubbed “Boris Island” – and opposes the expansion of Heathrow.

Mr Johnson said: “I think he’s a man of dynamism and greatness and he will seize the moment to give this country the long-term solution that it needs.

“It is plain the argument over aviation capacity is not going to vanish. You can’t long-grass this. It is necessary to come up with an answer.

“Business needs an answer and I’ve no doubt the Prime Minister is going to provide one. They have moved a long way. They have shown great foresight in abandoning a position that said no runways ever, and they are now looking at expanding aviation capacity.”

But Deputy Prime Minister Nick Clegg insisted the coalition would not back a third runway, although he acknowledged that ministers would have to consider other options to meet the country’s aviation needs.

“We’re not going to give the go-ahead to the third runway at Heathrow because we said very clearly, as both parties, that we wouldn’t do so,” the Liberal Democrat leader said.

“But that doesn’t mean we’re going to stick our heads in the sand over the aviation debate about capacity in this country.

“There are lots of ways of doing that and we shouldn’t just lurch to one solution because one individual MP was to say so.”