The expected government go-ahead for a third runway at Heathrow has been delayed by shortcomings in the recent public consultation on the development of the airport.

Ruth Kelly, transport secretary, said yesterday the government’s decision on the future expansion of Heathrow would be published “before the end of the year”.

The timetable has been extended by two months because of the need to conduct an “equalities impact assessment”, which was omitted from the three-month public consultation that closed at the end of ­February.

Failure to include the assessment in the original consultation had exposed the government to the risk of a judicial review.

The government has repeatedly made clear since publication of the aviation white paper in December 2003 that it supports the building of a third runway, as well as maximising use of the existing two runways at Heathrow, subject to meeting strict environmental conditions on local air quality and noise.

Ms Kelly said the department would now conduct a full equalities impact assessment under guidelines from the Equality and Human Rights Commission.

She said: “We want to be sure, given the socio-demographic mix in the Heathrow area, that we fully understand how airport development might affect different groups in terms of race, disability, age or gender.”

John Sauven, Greenpeace executive director, said the government was “having a massive runway wobble. Ministers are facing an inevitable legal challenge if they give the green light to Heathrow expansion because their public consultation was, quite frankly, fraudulent.”

“It sought to fix pollution data and marginalise the opposition of tens of thousands of people and the massive impact a new runway would have on our chances of tackling climate change.”

John Stewart, chairman of Hacan, the local residents group opposing the expansion of Heathrow, said Ms Kelly’s statement was “merely an attempt to try and forestall any legal challenge. It is a sign the government’s case for expansion remains very shaky indeed.”

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