The cost of abating the carbon impact of a proposed third runway at Heathrow has doubled since parliament approved the idea of expansion, a report presented to MPs suggests.

A study by the New Economics Foundation suggests the carbon value or cleanup cost of the runway has increased from £50bn to £100bn, twice the figure presented to ministers and parliamentarians by the Department for Transport in the Airports National Policy Statement (ANPS) in 2018.

The “carbon value” of the expansion is the price of abatement required to offset the carbon emissions of the runway. This autumn, the government revised carbon values to bring them into line with new legally binding net zero obligations, passed in June 2019.

The report – a draft of which was presented to members of the all-party parliamentary group on Heathrow expansion and regional connectivity – suggests these changes have a significant impact on the proposed runway expansion. “In a climate emergency, any project or policy which creates new greenhouse gas emissions comes at great cost to society. Either we suffer the consequences of deeper ecological collapse, or someone, somewhere, has to ‘clean up’ those gases,” the report said.

When a country, as the UK does, has a legal commitment to cut carbon emissions to zero, most options for reducing emissions and removing carbon from the atmosphere are already being utilised, the report said.

“The cost, therefore, of cleaning up, or ‘abating’, new emissions, gets higher as your climate ambition rises,” the report said.

In September, a new set of costs of carbon abatement were released by the government.

“Our calculations show that at Heathrow, the carbon cost of emissions resulting from the airport’s proposed expansion over the period 2025-2050 has doubled, from around £50bn, to over £100bn when considering the new government carbon values.” the report said. The carbon costs include that of both arriving and departing flights.

The change in costs impacts all proposed airport expansion. Across eight airports planning projects all have had their climate cost dramatically underestimated, NEF says.

The research suggested cumulatively the eight active airport expansion plans come with an emissions price tag of £73.6bn between 2025 and 2050.

Only a fraction of this, £11.8bn, is likely to be reclaimed in taxes on the aviation industry. The remainder, £62bn, will be a cost to government and represent “a colossal subsidy to polluting industry, and significant cost – either economic, environmental, or both – to the rest of society”, the report said.

David Simmonds MP, the co-chair of the APPG, said: “This report highlights the need to get the detail right when considering our future aviation picture and the government’s Jet Zero review.

“We cannot afford to underestimate the implications for major projects such as Heathrow expansion and future generations will not thank us for creating complicated financial mechanisms which won’t do anything to actually help the environment.”

Paul McGuinness, the chair of the No 3rd Runway Coalition, said: “As was perhaps inevitable, Heathrow expansion’s carbon costs have escalated exponentially, even before they’ve put more greenhouse gas emitting planes into our atmosphere. The ever-growing case for the government to cancel Heathrow expansion has become incontrovertible.”

When MPs voted for the Airline National Policy Statement, which contained the expansion in principle in 2018, the net economic value of it was between £3bn and -£2.5bn, he said.

Now the carbon abatement cost element of Heathrow expansion has increased exponentially, the total economic impact of the scheme can only come at a great cost to the UK economy, said McGuinness.

Lord Deben, the chair of the Climate Change Committee, which advises government, said last month: “There is not any space for airport expansion”.

The CCC recommends “no net expansion of UK airport capacity unless the sector is on track to sufficiently outperform its net emissions trajectory and can accommodate the additional demand”.

A Heathrow spokesperson said: “Reducing carbon emissions from flying has always been a central consideration of our plans to expand Heathrow.

“We have always known that we will have to prove that a new runway is compatible with the UK’s net zero target. While our current focus remains on responding to the pandemic, we remain confident that we can expand and meet stringent targets.

“The UK aviation sector was the first in the world to commit to net zero and publish a detailed plan to get there. The recent commitment by the whole global aviation sector to net zero and the UK government’s ambition for 10% sustainable aviation fuel by 2030 are clear steps towards taking the carbon out of flying, even as we grow.”