Proposals for a third runway at Heathrow could turn the skies over Hampshire and Surrey into “noise sewers”, claims an environmental pressure group.

This week, chancellor Rachel Reeves backed plans for an expansion at Heathrow Airport to boost economic growth in the country. She said the new runway would "make Britain the world's best connected place to do business".

The Farnborough Noise Group (FNG) has been campaigning for years against proposals to increase flight numbers at Farnborough Airport, as well as other airports in the region.

A spokesperson for the group warned that if the Heathrow expansion goes ahead, it would have a devastating impact on the area.

He said: “The rural areas like the South Downs and Surrey Hills are important for nature and for our wellbeing. The government plans to put the new flightpaths to support airport expansion specifically over these areas.

“The health impact of noise on health is well understood. We should be protecting the peace and quiet of our rural areas, not turning them into ‘noise sewers’. We have seen how businesses have used our rivers, we shouldn’t be doing the same to our skies.”

He also said as Surrey and Hampshire were at the intersection point for both Gatwick and Heathrow flightpaths, “expansion at both airports will have a quadrupling effect because the same areas are impacted by aircraft landing as well as taking off”.

The spokesman warned that the construction of a third runway at Heathrow risked becoming another HS2, referring to the proposed high-speed rail link from London to the North, which faced massive overspends and delays.

“By the time [the third runway] could be constructed, there will be tax on aviation fuel and the cost of emissions will be priced into tickets,” said the FNG spokesman.

“Inevitably there will be a reduction in the number of people flying. Flights cannot increase and still achieve the Government’s legally binding Net Zero target so new runways at both airports would end up being white elephants.”

At a recent meeting of the FNG at Zero Carbon Guildford, concerns were expressed that more flights at Farnborough, Heathrow and Gatwick would create more noise and air pollution.

The FNG refuted the Government’s argument that the third runway will be delivered in line with the climate obligations.

He said the expansion of Heathrow could have a knock-on effect at Farnborough Airport, as the increased flights at Heathrow and Gatwick might lead to congestion, potentially limiting the availability of slots for Farnborough Airport flights.

A spokesperson for the group added: “From the Farnborough perspective, Heathrow and Gatwick want to use the airspace Farnborough currently has. If Gatwick gets a second runway and Heathrow a third, the will not be space for Farnborough's flightpaths.

The mayor of London, Sadiq Khan, also opposed the Heathrow expansion.

“Despite the progress that's been made in the aviation sector to make it more sustainable, I’m simply not convinced that you can have hundreds of thousands of additional flights at Heathrow every year without a hugely damaging impact on our environment,” he said.