Prime minister David Cameron must decide whether he is a “man or a mouse” and push ahead with the third runway at London Heathrow Airport, according to Conservative MP Tim Yeo.

Writing in the Telegraph, Yeo argues Cameron must “find his sense of mission” and push ahead with the controversial project.

The Conservative party has ruled out a third runway at the hub airport in south-east England as it continues a consultation into aviation policy.

Yeo, a former environment minister and head of the Parliamentary climate change committee, is however among a growing number of Conservative MPs voicing opposition to the party line.

He argued environmental concerns over the proposed development are “disappearing”.

Yeo challenged: “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?

“An immediate go-ahead for a third runway will symbolise the start of a new era, the moment the Cameron government found its sense of mission. Let’s go for it.”

Housing minister Grant Shapps last week said Britain should consider building a third runway at Heathrow.

George Osborne, the Chancellor, is also thought to share the view.

However, transport secretary Justine Greening said earlier today there was a “political consensus” against a new runway, adding the coalition agreement between the Conservatives and the Liberal Democrats rules out any expansion before the next election.

Labour also currently opposes the idea of a third runway.