MPs have called on the government not to support the construction of a third runway at Heathrow unless several environmental conditions are met.
Earlier in the year, the Airports Commission recommended a third Heathrow runway as the preferred option to ease passenger and air traffic in the South East, beating the extension of Heathrow's north runway, a second Gatwick runway and a completely new airport in the Thames Estuary.
Now, the Commons Environmental Audit Committee says that concerns over climate-changing emissions, air quality and noise pollution must be addressed before the government can support Heathrow's expansion. The government is due to announce its stance on the matter by the end of the year.
Dealing with the environmental conditions at a later date would be "irresponsible", said chair of the committee and Labour MP, Huw Irranca-Davies.
He said it "could lead to legal challenges as a result of the potential damage to public health from increased air pollution and noise".
"If the government decides to accept the commission's recommendation for a third runway in principle, we will seek assurances from the secretary of state for transport that environmental conditions will be met before it is given final approval," he added.
The Committee backed the Airports Commission's calls for flights between 23:00 and 06:00 to be banned in a bid to ease noise pollution. But it also said that Heathrow needed to demonstrate that it an extra runway would in fact be quieter than it currently is.
Mr Irranca-Davies said: "The communities living near to the roads around Heathrow already put up with noise and extra traffic.
"It would be quite unacceptable to subject them to a potentially significant deterioration in air quality as well."
