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.

Ministers can ask the CCC for ad-hoc advice on specific policy issues but is under no legal duty to follow it.

Lord Deben, a former CCC chairman, said there was “limited space for aviation growth” without emissions reductions.

“If they give planning permission for expansion of Heathrow that inevitably means there will be less opportunity for other airports in Britain,” Lord Deben said.

“This must be a sensible, logical decision and the CCC must be involved in giving advice.”

Greenpeace UK said there was an obvious need for independent experts at the committee “to assess the real risks and costs of any expansion”.

“Any attempt to side-step them would show a complete lack of confidence in Labour’s stated position regarding the tests a new runway needs to pass, and more importantly, miss the legal requirement for UK carbon reductions,” Dr Douglas Parr, policy director for Greenpeace UK, said.

The CCC also told the BBC it had not been asked to provide advice on any future expansion of Gatwick Airport.

A decision on a proposed second runway at Gatwick is expected in the coming weeks after Transport Secretary Heidi Alexander said she was “minded to approve” the expansion in February.

Chancellor Rachel Reeves announced the Labour government was backing plans for a third runway at Heathrow in January this year.

Reeves said Heathrow expansion, delayed for decades over environmental concerns, would “make Britain the world’s best connected place to do business” and boost economic growth.

At the time, the government said the expansion “must be delivered in line with the UK’s legal, environmental and climate obligations”.

The expansion of Heathrow has long been opposed by green groups and it is expected to face resistance and probably legal challenges, not least because of its environmental impact.

In July, the CEO of Heathrow Airport, Thomas Woldbye, insisted the expansion proposal was in line with the aviation industry’s target to be net zero by 2050.

But he acknowledged that planning permission would not be granted by the government unless legal limits of emissions were adhered to.

The government wants to review planning guidelines that will shape its decisions to expand Heathrow, Gatwick and other major airports.

Giving evidence to MPs this week, the CCC’s chief economist, Dr James Richardson, said it wasn’t too late to influence the review, which has not been launched yet.

But Labour MP Barry Gardiner said he was seriously worried the CCC was “acquiescing in what the government is planning for aviation”.

He questioned why the government had not sought the CCC’s advice before announcing its support for Heathrow’s expansion.

The Climate Change Committee gave its most recent advice on aviation emissions in the Seventh Carbon Budget.

The budget, published in February, said the sector can reach net zero through the roll-out of sustainable aviation fuel, the electrification of planes, and managing growth in demand for flights.

But the committee suggested limiting airport expansion to reduce emissions and warned the development of low-carbon aviation technologies was “uncertain”.

“The aviation sector needs to take responsibility for its emissions reaching net zero by 2050,” the committee said.

“The cost of decarbonising aviation and addressing non-CO2 effects should be reflected in the cost to fly. This will help manage growth in aviation demand in line with net zero.”

A Department for Transport spokesperson said: “The government is assessing initial proposals on Heathrow expansion – a significant step towards unlocking growth, creating jobs, and delivering vital national infrastructure to drive forward our Plan for Change.

“The assessment of proposals is being conducted to support the forthcoming Airports National Policy Statement review, and we will engage the Climate Change Committee throughout this process.

“We have been clear any airport expansion proposals need to demonstrate they contribute to economic growth, can be delivered in line with the UK’s legally binding climate change commitments, and meet strict environmental requirements on air quality and noise pollution.”

Additional reporting by BBC transport correspondent Katy Austin