A third runway at Heathrow Airport will be a white elephant unless aviation is made "greener", a think-tank group has said.
The Government is expected to decide within days whether the west London airport should be expanded to accommodate an extra short runway.
The Institute of Public Policy Research said the Government should not commit to a third runway unless the aviation industry's own emissions targets were guaranteed for any aircraft which wanted to use the new runway.
The institute added that the Government should require aircraft using the runway to meet the industry targets to cut carbon dioxide emissions and noise in new aircraft by 50% and nitrogen oxides by 80% by 2020.
The Institute's climate change head, Simon Retallack, went on: "The economic advantages of building a third runway at Heathrow have been greatly overstated and the environmental case against it is overwhelming. If ministers were to give the runway a green light, this should only be with strict conditions for meeting tough air quality, noise and climate change targets."
He continued: "The aviation industry has pledged to cut carbon dioxide emissions and noise in new aircraft by 50% and nitrogen oxides by 80% by 2020. Only aircraft which meet or exceed those targets should be permitted to land on any new runway.
"(Heathrow operator) BAA and the airline industry must bear the risk that a third runway will be a white elephant if aviation cannot be made greener.
"If a third runway is built without these conditions attached, European air quality standards will continue to be breached, noise pollution for households on flight paths will increase and a valuable opportunity will be missed to ensure the aviation industry prepares for a low carbon future."
Although the Conservatives have recently come out against a third runway, the Government has consistently backed the plan. The Government had been due to make a decision about Heathrow before Christmas but the date was put back to some time in January by Transport Secretary Geoff Hoon.
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Prime Minister Gordon Brown is now thought ready to give the go-ahead to the controversial scheme. An announcement on the plan is tipped for the middle of this week, as long as it is approved by the Cabinet on Tuesday.
