LONDON - Thousands of people across London could be exposed to worse levels of noise, air quality and traffic congestion by the building of a proposed third runway at Heathrow, already one of the world's busiest airports, a committee of MPs warned Friday.

The powerful House of Commons Transport Committee told the government there must be sufficient measures to protect or compensate Londoners affected by the project.

In their report the MPs said they recognised the efforts made by the government and Heathrow Airport Ltd to mitigate the significant social and environmental impacts arising from expansion at Heathrow.

But they added more safeguards are needed to ensure that the interests of passengers are protected, and the adverse environmental, social and health impacts on affected communities are addressed.

Lilian Greenwood, chair of the committee, said the third runway project, is the highest cost expansion option and one of the largest privately financed infrastructure projects anywhere in the world.

The MP added that at present, the draft Airports National Policy Statement (NPS), does not guarantee that passengers will be protected from the cost risks associated with the scheme.

Greenwood said Transport Secretary Chris Grayling must set out how airport charges at Heathrow will be held down.

She said a list of recommendations made by her committee to the government will improve the NPS and reduce the chance of a successful legal challenge.

Greenwood said: "The government and Heathrow have made efforts to mitigate the significant impacts, but safeguards on air quality, surface access, connectivity, costs and charges and noise should be strengthened. As a matter of urgency, we also want to see how the government plans to deliver the necessary airspace change. This must all be done before a final NPS is tabled for approval by both Houses of Parliament."

The Transport Committee said the government now has the opportunity to make changes to the NPS, before it is laid before both Houses of Parliament for debate. "The Committee accepted there was a case for additional runway capacity, particularly hub capacity and that expansion at Heathrow could deliver the government's strategic objectives for greater connectivity for passengers and freight."