An "inflated" economic case for a third runway at Heathrow was presented by the Airports Commission , a new report claims.

The committee, which recommended expansion of the airport in July, is also accused of underplaying legal, environmental and social factors which make a new landing strip "undeliverable".

Hillingdon , Richmond, Wandsworth, and Windsor and Maidenhead councils have jointly published their official response to the commission's findings, which they claim undermines the case for a bigger Heathrow.

The councils, which are members of the 2M Group of local authorities opposed to Heathrow expansion, have sent the report to MPs as the Government prepares to announce its plans for aviation expansion.

Hillingdon Council leader Ray Puddifoot said: "The critical factors which present the biggest challenge to a potential third runway have been either avoided, or worse, misinterpreted by the commission.

"There is a distinct lack of information on air quality and flight paths and instead there are inflated claims about a colossal economic windfall that the commission says will come from a handful of new trade routes.

Leader of Hillingdon Council, Cllr Ray Puddifoot

"It's clear to me that the case for expansion at Heathrow doesn't add up and a third runway will never happen, no ifs or buts."

The councils' report challenges the commission's findings that a third runway would add up to £147bn to Britain's GDP.

It claims the commission's own expert advisor panel dismissed that figure, pointing to "extreme assumptions" and "exaggeration".

A more accurate figure, it argues, is the conventional Treasury growth forecasting model, which predicts a boost to the economy of £33.6bn-£54.8bn - similar to the £27.2bn-£47.1bn estimated for a second runway at Gatwick.

The report also takes issue with the commission's conclusion that a bigger Heathrow would be a "better neighbour for local communities".

It questions how this can be the case when, according to the councils' report, the commission's own modelling estimates 160,000 new people would be exposed to aircraft noise.

The airport claims fewer people would be affected by noise with a third runway than at present, due to quieter planes, steeper landing paths and other innovations.

The commission concluded that a new runway would not increase noise above current levels.

Responding to the councils' report, a Heathrow spokeswoman said: "Following a £20 million, two and a half year detailed study of where the next runway should be, the Government's independent Airports Commission has unanimously and unambiguously confirmed that a third runway at Heathrow can make the airport a better neighbour.

"The report made it clear that Heathrow can meet air quality limits, remain within carbon targets and reduce the number of people impacted by noise compared to today."

* You can read the councils' report in full at www.hillingdon.gov.uk/heathrow .