The UK Government needs to decide on a carbon reduction plan before it makes a decision on Heathrow.
Mary Creagh MP, Environmental Audit Committee (EAC) Chair, said so in response to a letter from Transport Secretary Chris Grayling regarding the proposed runway expansion at the airport.
In the letter, Mr Grayling says the UK does not yet have any legally binding aviation emission targets due to uncertainty as to how these would be allocated amongst the other countries that fly into and out of the country.
He adds the UK will follow the Climate Change Act, which requires aviation emissions to be taken into account when setting carbon budgets and aims for an overall 80% emissions reduction by 2050 based on 1990 levels.
He also said the Committee on Climate Change (CCC) has drawn up a planning assumption for emissions levels through to 2050 but UK Government may not accept this.
According to Mr Grayling, the Airports Commission says measures are available to meet the CCC planning assumption aviation targets anyway, even with demand growth of more than 60% and without requiring other sectors to compensate.
Ms Creagh, said: “The government has said that Heathrow can be delivered within carbon limits, yet this letter shows it has not yet decided what those international aviation emission limits should be.
“This implies it is considering rejecting the advice of the independent Committee on Climate Change. The government should set out its strategy to limit carbon emissions from international aviation before taking a final decision on Heathrow expansion.”
The EAC today urged Prime Minister Theresa May to challenge Donald Trump on his climate change stance.