Senior Conservative Tim Yeo has goaded David Cameron over the expansion of Heathrow airport, urging him to decide if he is "a man or a mouse".
The former environment minister, who chairs the Commons energy committee, insists that environmental objections to calls for a third runway are disappearing and claimed backing the move would give the government a "sense of mission".
In a stinging attack he questioned whether the prime minister would preside "over a dignified slide towards insignificance" and suggested the leader's heart was "impenetrable" to most voters.
In an article for The Daily Telegraph he wrote: "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?
"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."
It comes after housing minister Grant Shapps warned a third runway was needed to ensure the UK remained a "great trading nation" and Mayor of London Boris Johnson accused Cameron of "pussyfooting around" on expansion.
Yeo was previously a high profile opponent of expansion but now argues European Union carbon emissions caps will force airlines to use more environmentally friendly planes if they want to use new capacity at Heathrow.
He added: "The environmental objections are disappearing. Last January, greenhouse gas emissions from flying were brought within the EU cap.
"Indeed, we could cover the whole of Surrey with runways and not increase emissions by a single kilogram - if Heathrow expands, so remaining the European destination of choice, airlines will fly their newest and quietest aircraft to it."
In the run up to the 2010 general election the Conservatives decided to oppose plans to expand Heathrow, with Cameron declaring: "No ifs, no buts, no third runway".
But Yeo insists that the prime minister should not be afraid of changing his mind. "The prime minister is, I suspect, nervous of being attacked for another U-turn," he said.
"But this isn’t a tax wheeze unveiled on Budget Day and consigned to the dustbin before Whitsun. It is an evidence-based reappraisal of a transport infrastructure that looks increasingly Third World compared with much of Asia."
One major barrier to a U-turn over Heathrow is the opposition of transport secretary Justine Greening, who led the campaign against the airport's expansion while in opposition.
Greening, whose Putney constituency lies underneath the Heathrow flight path, told the BBC on Tuesday morning that a third runway "would not be "the right thing for Britain".
Asked if she could continue to serve in the cabinet if she was overruled by the prime minister on the issue she said: "I think it would be difficult for me to do that."