A third runway at Heathrow could be built without adding to noise or pollution, according to a new report.

But campaigners fighting expansion of the airport have branded the findings "ivory tower research" and say the authors are "not living in the real world".

The Independent Transport Commission (ITC), which commissioned the study, claims it shows concerns over noise, CO2 emissions and local air quality should not prevent a new runway being built at either Heathrow or Gatwick.

Sustainability experts Peter Hind and RDC Aviation Ltd, which carried out the research, concluded that technological advances meant more flights would not necessarily mean more noise and more pollution.

They forecast a 1.6% annual improvement in the fuel efficiency of planes would lead to a steady fall in carbon emissions.

They also predicted that quieter planes and changes to airport operations would help reduce the noise experienced by those living under the flight paths.

As for local air pollution, including levels of harmful NO2, they said this could be addressed by encouraging more passengers to travel by public transport.

'Sustainability concerns should not stop airport expansion'

Dr Stephen Hickey, chair of the ITC's aviation working group and ITC commissioner, said: "Having reviewed these important sustainability issues in-depth, it is clear that the environmental challenges of limiting the carbon emissions, noise and local air quality impacts can be tackled.

"Whether the government pursues the proposal to expand Gatwick or Heathrow, the ITC research demonstrates that sustainability concerns should not stop the UK realising the great additional benefits that increased connectivity can provide."

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Dr Hickey added that the government could play its part by appointing an independent regulator to monitor and take action over "sensitive" issues like noise.

The ITC describes itself as Britain's foremost transport think tank. Its "core benefactors" include both Gatwick and Heathrow airports.

'Not living in the real world'

John Stewart, who chairs the anti-Heathrow expansion campaign group HACAN, dismissed the findings, claiming the authors were "not living in the real world".

"The report repeats the myth that the noise climate around major airports has improved. But this is not living in the real world.

"You can only argue the climate is better if you ignore the significant rise in the number of planes passing over people's homes.

Anti-expansion campaigners stage a silent protest at Heathrow in 2015 about air pollution

"The report is right to say that individual aircraft have become less noisy but for most residents this is off-set by the sheer rise in the number of planes. I fear this is ivory tower research."

Mr Stewart added that the report "skates too easily" over the impact of an extra 250,000 flight a year at Heathrow with a third runway, though he did welcome its recommendation for an independent noise regulator.

'Poor air quality is a national problem requiring government action'

Heathrow welcomed the report, which it said recognised its work to get more passengers travelling by public transport.

Matt Gorman, the airport's director of sustainability, said: "Heathrow takes air quality issues seriously. This report adds to the evidence presented by the Airports Commission that road traffic is the main contributor to poor air quality and it is a national problem which needs government action.

"Heathrow has worked to maintain airport-related traffic broadly static since the 1990s and is taking action to reduce emissions further by switching to electric vehicles and increasing public transport options for passengers and colleagues.

"Heathrow has called for local and national partners to work together on a plan to reduce the impact of non-airport related vehicles, which are the major source of local air pollution.

Matt Gorman confronts a protester outside the Heathrow director's home in 2015

"The huge benefits of additional capacity at our airport need not come at the expense of the environment – Heathrow expansion can deliver for both."

Jock Lowe, director of Heathrow Hub, which proposes extending the northern runway, also welcomed the report, which it said recognised how its plans would reduce the number of people affected by aircraft noise.

The Airports Commission recommended last summer that a third runway should be built at Heathrow, provided a number of conditions could be met.

The government announced in December that it was postponing its decision by six months to allow time for further research on the evironmental impact of expansion at either Gatwick or Heathrow.