Heathrow risks losing a legal challenge against its third runway unless it meets a raft of tough conditions on landing charges, pollution and public transport, an influential committee of MPs has warned.

The transport select committee believes Heathrow and the Government must put more stringent stipulations on the north west runway expansion project to ensure an expected legal challenge by opponents is unsuccessful and to prevent passengers being hit in the pocket.

Its final report on the draft National Policy Statement (NPS), which forms part of the planning process for large infrastructure schemes, the committee has recommended various measures it believes are vital for the project to stand up to a judicial review.

Among its large number of recommendations, it calls for airport charges - which are "already the highest in the world" at Heathrow - to be held flat in real terms, more stringent testing of whether the scheme will meet air quality legislation and a condition that approval for the scheme only be given if the target for there being no more airport-related traffic than today can be met.

It is also concerned about the "absence of detail" surrounding changes to the M25.

Chairman Lillian Greenwood, the Labour member for Nottingham South, said while her committee had effectively supported the need for a third runway, the report highlighted several areas of concern where the Government “needs to do more”.

“We think this will save them from facing successful legal challenges,” she said. “It is better to get these things sorted now.

"It is really important the Government protects passengers from scheme costs and higher airport charges. We are calling on the Government to make sure airport users are not on the rough end of the deal."

The Government must decide whether to implement the Transport Committee’s recommendations and, if it does so, add them to the final NPS which goes before a vote in Parliament in July.

Once an NPS has been voted through by MPs, there is a six-week window when legal challenges to it can be made. These challenges cannot be based on the content of the NPS itself, as this will have been approved by Parliament, but rather the procedure that led to the NPS being approved. A group of four councils - Hillingdon, Richmond, Windsor and Maidenhead, and Wandsworth - are understood to be preparing a challenge to the scheme.

At present, both Heathrow and the Transport Secretary have made pledges to meet various goals, such as keeping landing charges close to current levels. But the Transport Committee wants these shored up with formal guidelines because it fears verbal promises would not stand up to the scrutiny of a judicial review.