Tories set for a U-turn over opposition to third runway at Heathrow

A consultation on airport capacity has been delayed, allowing a decision after the election

The Conservatives are preparing for a controversial U-turn over their opposition to building a third runway at Heathrow.

The party strongly opposed the expansion of Britain's busiest airport at the last election and the Coalition Agreement ruled out the construction of extra runways at Heathrow, Gatwick or Stansted.

But senior Tories expect to leave open the option of a new runway at Heathrow in response to fears that lack of airport capacity in the South-east of England is undermining Britain's economic competitiveness.

George Osborne, the Chancellor, has been pressing for a change of heart over Heathrow's expansion.

However, Justine Greening, the Transport Secretary, is a strong opponent of the move – not least because her west London constituency is under the airport's flight-path. The Liberal Democrats, as well as several prominent Tory MPs including Zac Goldsmith, also remain resolutely against expanding Heathrow.

Problems over the policy were underlined when Ms Greening scrapped plans to begin a consultation yesterday on future airport capacity in the South-east. It has been delayed until the autumn at the earliest, signalling that final decisions over how to cater for increased numbers of flights have been put off until after the general election expected in 2015.

The latest delay was condemned by the CBI's director general, John Cridland. "We have no time to lose in getting on with solving the UK's aviation capacity issues, if we are to double our exports by 2020," Mr Cridland said.

"Everyone understands this is a difficult issue, and not one with any easy answers. However, political deadlock is getting us nowhere."

Mr Osborne has cooled on the idea of building a new airport in the Thames estuary – either the "Boris Island" plan backed by London Mayor Boris Johnson or a £50bn proposal for an airport near the Kent coast – on cost grounds, as well as the time it would take to build. An ally of the Chancellor said: "Justine Greening needs to realise that if you are a cabinet minister, you have a wider responsibility than being just a constituency MP."

Asked if anything had been ruled out, the Prime Minister's spokesman said: "We have not even begun the process yet, that is something for later in the year, so we will set out the position then. We are asking people for their views."