"The prime minister must ask himself whether he is man or mouse," lawmaker Tim Yeo wrote in The Daily Telegraph, a Conservative-supporting newspaper that splashed the question in a front-page headline.
Tuesday's blast was the rudest shot yet in a campaign by airlines, business groups and unions demanding that Cameron ditch his opposition to a third runway at Heathrow, Europe's busiest airport, which serves 70 million passengers a year.
Business groups back the third runway as job-creating economic boost for the flat-lining British economy. There are also worries that Heathrow is losing ground against competitors such as Frankfurt airport and Charles de Gaulle airport in Paris.
Opposition to the third runway was Cameron's initiative four years ago as he worked to make his party appear more sensitive to environmental issues. Justine Greening, Cameron's transport secretary, supports her constituents in west London in opposing another runway.
Greening's department is setting long-term goals for preserving London's status as an aviation hub. But conclusions won't be published until March and only then would the department look at specific moves to increase capacity.
The recent pressure on Cameron is partly in anticipation of a shuffle of Cabinet positions. Dismissing
"Does he want to be another Harold Macmillan (prime minister 1957-1963), presiding over a dignified slide towards insignificance? Or is there somewhere in his heart ... a trace of (Margaret) Thatcher, determined to reverse the direction of our ship?" Yeo wrote in his op-ed piece.
Cameron's office said the prime minister would keep his promise to oppose another runway during his coalition government with the Liberal Democrats, which is due to end in 2015.
"We don't see the argument for a third runway," a spokeswoman for Cameron said, speaking on condition of anonymity.
Still, the Institute of Directors, representing 38,000 directors of U.K. businesses, weighed in to support Yeo.
"There is no doubt that we need more airport capacity, and the longer the government delays deciding where it will be, the more chances for trade we will miss," said Simon Walker, the Institute's director general.
British Airways, the biggest tenant at Heathrow, has been equally forceful in pressing Cameron to change direction.
"I don't believe this government has the political will to address the issues," Willie Walsh, chief executive of International Airlines Group, BA's owner, said last month.
"David Cameron seems a lot happier clapping and cheering for (Olympic) gold medals than dealing with tough, long-term economic challenges," Walsh told the Financial Times.
London Mayor Boris Johnson, a potential rival to Cameron, wants to build an entirely new airport—dubbed "Boris Island"—east of London near the mouth of the River Thames.
"Heathrow is fundamentally not the place" for expansion, he has said.
Heathrow, the hub of long-haul flights, is operating at capacity, with 1,300 landings and takeoffs every day. Whatever happens, airlines could not expect any additional capacity at Heathrow or any other London airport before 2020.
Gordon Brown's Labour government approved a third runway for Heathrow in 2009, in the face of loud opposition from locals.
Cameron canceled the project when he formed a coalition government following the 2010 election. Labour's new leader, Ed Miliband, has reversed his party's support for a third runway as well.
A study published by the British Chambers of Commerce earlier this year claimed that a third runway would add 30 billion pounds ($48 billion) a year to the U.K. economy, and that every year of delay cost the nation about 1 billion pounds ($1.6 billion).