Boris Johnson and Zac Goldsmith warn government against Heathrow U-turn in wake of cabinet reshuffle
David Cameron's attempts to defuse the growing political storm over airport capacity in London are floundering after renewed criticism from the mayor of London and a threat by a high-profile Conservative MP to trigger a byelection if the government performs a U-turn and decides to go ahead with a third runway at Heathrow.
Boris Johnson demanded on Wednesday that the Tories make a pledge not to expand Heathrow that would last beyond the next election, while Zac Goldsmith, a former environmental adviser to the prime minister, said he would force a byelection in his Richmond Park and North Kingston constituency if it went ahead.
The Conservatives said in their pre-election manifesto they would stop a third runway being built at Heathrow, but the departure in the cabinet reshuffle of Justine Greening, who as transport secretary campaigned vigorously against expansion, was seen as removing an obstacle to a change in policy.
The new Conservative co-chair, Grant Shapps, reinforced that impression on Wednesday when he said there would be no expansion during this parliament in line with the coalition agreement, but refused to rule it out in future.
"If we are going to remain a great trading nation in the future, you need to have ports. Airports are particularly important these days and there are a lack of slots in the south-east around London and it must be addressed, otherwise we are dooming ourselves to economic failure in the future," he told BBC Radio 4's Today programme.
Shapps said it would be "irresponsible" not to look at how to boost aviation capacity, adding the government would not "turn a blind eye" to infrastructure improvements that would help the economy to grow.
His promise to consider all options did little to alleviate the impression among critics that the Tories are ready to give a third runway the green light.
Johnson, who wants a new airport to be built in the Thames estuary, called for the government to promise there would be no third runway even after the next election.
He said: "There are much, much better solutions that would deliver long-term growth and jobs and I think what we need to do now is end the uncertainty about Heathrow, end this anxiety that's now building up that a U-turn is in progress and say, 'No folks, it's all right, the policy is as it has been, which is to say no to the third runway both now and in the future - ie beyond the next two-and-a-half years.'"
The London mayor had already criticised the demotion of Greening in the strongest terms, citing it as evidence that "the government wants to ditch promises and send yet more planes over central London".
Johnson was joined in his criticism by Goldsmith, whose constituency lies beneath the Heathrow flight path. "I think it is impossible to pretend that this isn't a sign," he told the Today programme.
"We haven't just lost Justine Greening from this department, we have also seen Theresa Villiers moved out, both of whom were absolutely rock-solid on this issue in terms of defending what is still the government's line officially.
"I think their movement out of the Department of Transport shows the government is at least trying to open the door to the possibility of a third runway."
The deputy prime minister, Nick Clegg, said the Liberal Democrats stood by the coalition agreement and the promise in its own manifesto not to build a third runway during the current parliament but added: "The Conservatives can change their stance in whatever way they want."
He said his view was that building links with growing economies should not be done "at any old environmental cost".
Shapps also faced questions on Wednesday over whether the appointment as environment secretary of Owen Paterson – who is opposed to wind farms and reportedly in favour of fast-tracking shale gas exploitation – would lead to a watering down of the coalition's promises on the environment. But the Tory co-chair said: "We will be the greenest government ever."