The UK government's climate change advisory panel has said it has not yet been asked to formally assess how plans to expand Heathrow airport would impact on carbon emissions targets.
The Climate Change Committee (CCC) told the BBC it would give a view on plans to build a third runway at Heathrow if advice was requested.
The government said the expansion must not breach the UK's legally binding target of lowering emissions to net zero by 2050.
The CCC is required by law to assess whether the target will be met and it has repeatedly cautioned against airport expansion.
The government said it was assessing initial proposals on Heathrow expansion and would engage with the committee during the process.
