Heathrow runway back on agenda – but not before 2015

David Cameron put the possibility of building a third runway at Heathrow back on the Tory agenda yesterday as the Government prepares to set out its plans for boosting airport capacity in the south-east of England.

The Conservatives opposed the construction of another runway at the UK's busiest airport in their last manifesto – not least because of the number of marginal seats in south-west London. The Coalition Agreement also rules out the prospect of a U-turn on the subject during this Parliament.

However, Tory sources confirmed last night that the argument over the merits of a third runway was a "live issue" for the party as it considered transport policies after 2015. More immediately the Government is expected to raise the prospect of expanding Heathrow in a white paper due in the next month on aviation policy.

In the Commons yesterday, Mr Cameron said the Government "must not be blind" to the need to increase the number of flights that airports can handle. But the Transport Secretary, Justine Greening, whose Putney constituency is beneath Heathrow's flight-path, is a vehement opponent of the airport's expansion.

Mr Cameron was tackled in the Commons yesterday on the subject by the Conservative MP Zac Goldsmith, whose Richmond Park constituency is also close to Heathrow.

The Prime Minister replied: "Clearly we must not be blind to two important considerations. One is how we expand airport capacity overall, but secondly how do we make sure that Heathrow operates better."

Eric Pickles, the Communities Secretary, also only ruled out expansion of Heathrow until 2015. He said: "I am pretty clear – there is not any chance of us reopening the third runway within this parliament."

Joss Garman, a campaigner at Greenpeace, said Mr Cameron's "refusal to give unequivocal line" on Heathrow could lead to the "mother of all U-turns".

Meanwhile, Conservative sources denied a report that the Government was cooling over its commitment to build a high-speed rail link between London and Birmingham.