DAVID Cameron's promise to oppose Heathrow expansion must be honoured as a Government-commissioned report contains "342 pages of ifs and buts", MPs have heard.

Conservative Tania Mathias argued the case for a third runway has not been successfully made despite the Airports Commission's recommendation.

The Twickenham MP raised concerns over the costs of the projects and the noise impact on residents living close to the airport.

And she recalled the Prime Minister's pledge in 2009 when, as opposition leader, he declared a third runway at Heathrow "is not going ahead, no ifs, no buts".

Earlier this year the Airports Commission picked Heathrow for expansion over Gatwick. However, it will now be up to the government to make the final decision.

Moving a debate on the final report of the Airports Commission, which examined how to boost airport capacity in the UK, Ms Mathias told the Commons that Heathrow "cannot be the hub it aspires to be".

She said: "The Prime Minister in 2009, when leader of the opposition, said 'no ifs, no buts, no third runway'. This is 342 pages of ifs and buts.

"It is not a solution for the UK's future aviation needs and before the Government makes its decision I would urge it to remember the promise of the Prime Minister."

Former transport minister Sadiq Khan, Labour's London mayoral candidate, said there is a need to increase airport capacity in the south-east.

He backs a new runway at Gatwick rather than Heathrow expansion.

Conservative Simon Burns, also a former transport minister, asked Mr Khan: "Could you please tell me when was it that you changed your mind on Heathrow given that you were a transport minister under a Labour administration that opted for a third runway at Heathrow, and you fought the 2010 general election on a pledge that a Labour government would build a third runway at Heathrow?"

Mr Khan (Tooting) said he listened to the points raised in the Airport Commission, adding: "But also I've read the Supreme Court judgment.

"I've met some of the teachers who can't teach during the daytime because of the noise in those classrooms in west London. I've met those who took the case to the Supreme Court.

"I've met some of the children struggling and also met some of those struggling from ill-health in London.

"But the challenge is: how do we address the need for increased flight capacity? A case I still accept now that we have in this part of the country."