Any expansion at Gatwick or Heathrow airports would be illegal in terms of pollution and damaging to human health, the Green Party has said.

Any major new runways would be "bad news for air quality and result in an unprecedented increase in noise levels" said Keith Taylor, Green Party MEP for the South East.

The party's comments came as it responded to the consultation launched by the Whitehall-appointed Airports Commission following its air quality assessment of the Heathrow and Gatwick expansion options.

The commission is due to make a final recommendation to the Government in the next few weeks on which of the three short-listed schemes - two at Heathrow and one at Gatwick - should go ahead.

The Green Party, local councils around Heathrow and the Gatwick Area Conservation Campaign are telling the commission it has underestimated the future environmental impacts of airport expansion.

But Heathrow Ltd, which put forward one of the two Heathrow schemes, said the commission's assessment "confirmed an expanded Heathrow will go beyond meeting local air quality limits".

Gatwick's bosses, on the other hand, believe the West Sussex airport has the edge on Heathrow in terms of legal air quality limits.

Chaired by Sir Howard Davies, the commission issued a further air quality assessment after the UK's Supreme Court last month set a deadline for the Government to produce new plans for reducing air pollution levels.

Mr Taylor said: "Sir Howard could hold 100 consultations if he wanted but the reality is that building any major new runways would be seriously bad news for air quality, rule out any chance of meeting our climate change targets, and would result in an unprecedented increase in noise levels."

The 2M Group - a cross-party body of councils surrounding Heathrow - said the commission's assessment estimated pollution levels up to 2030 but that was around 20 years before any expanded airport would reach full capacity.

Hillingdon Council leader Ray Puddifoot described the assessment as "not credible or realistic".

Heathrow Airport Ltd submitted its response to the commission's consultation.

Heathrow's sustainability and environment director Matt Gorman said: "The commission's air quality analysis has confirmed an expanded Heathrow will go beyond meeting local air quality limits.

"We worked with local communities and campaign groups so that our new approach to Heathrow expansion would deliver the right environmental solution as well as the right solution for the economy. Now let's get on with it."

Gatwick chief executive Stewart Wingate said: "The recent Supreme Court ruling means air quality is now even more fundamental to the decision on airport expansion.

"Heathrow currently breaches legal air quality limits and it defies common sense that a third (Heathrow) runway will solve the problem. In contrast, Gatwick has never breached legal air quality limits and its location means it can guarantee that it never will."

Gatwick Area Conservation Campaign chairman Brendon Sewill said: "The commission are seriously underestimating future pollution levels.

"Expanding Gatwick will inevitably increase pollution due to lack of infrastructure - infrastructure that can't be improved."

Reigate MP Crispin Blunt, chairman of the Gatwick Co-ordination Group - a group of Conservative MPs, said: "Gatwick expansion would be a disaster for the local area. It is now clear that Gatwick's own assessments of the air quality impact of a new runway are completely unreliable.

"This adds to the data already established in the consultation that Gatwick's plan would ruin thousands of lives and push local services and infrastructure beyond their limits."