Patrick McLoughlin has downgraded the government's guarantee of a decision on airport expansion in summer 2016 to a "hopefully". The transport secretary made the admission after David Cameron came under fire from business groups on the night of 10 December for kicking the issue of building a third runway at Heathrow Airport into the long grass.

"We accept that additional airport capacity is needed and we will make a decision on where we are going on that hopefully in the summer of next year," McLoughlin told BBC Radio 4's Today programme.

The prime minister faced considerable pressure from Conservative MPs, the Mayor of London Boris Johnson, and the Tories' Mayoral candidate Zac Goldsmith, who urged Cameron to reject the Airports Commission's recommendation of expanding the west London site. The Conservative leader also infamously promised in 2009 that with "no ifs, no buts" he would block an expansion of Heathrow.

The delay has proved to be very controversial and John Longworth, director-general at the British Chambers of Commerce, described the move as "gutless". Longworth said: "Businesses will see this as a gutless move by a government that promised a clear decision on a new runway by the end of the year. Business will question whether ministers are delaying critical upgrades to our national infrastructure for legitimate reasons, or to satisfy short-term political interests.

"Businesses across Britain will be asking whether there is any point in setting up an Airports Commission – or the recently-announced National Infrastructure Commission – if political considerations are always going to trump big decisions in the national interest."

Sadiq Khan, Labour's Mayoral candidate, argued that the UK economy could not "afford more dithering" and claimed Gatwick Airport would be a better site for expansion.

"Businesses desperately need more airport capacity around London, and the Tories are letting them down. Gatwick stands ready to deliver it sooner, at a lower public expense and without the damaging impact of Heathrow expansion," Kahn said.

"We already know Heathrow can't be the solution. The additional damage from air and noise pollution would mean more years of delay, while protracted legal battles are fought. It must be Gatwick – and we need to get on with it."