Failure to include plans for a third runway at Heathrow from the Tory manifesto "won't fool anyone", the Liberal Democrats have warned.

According to The Sunday Telegraph, Tory MPs have threatened to reject their own manifesto if it promises to expand the major hub.

During the 2010 General Election campaign the Conservatives pledged a third runway would not be built at Heathrow, however the Prime Minister has now backed the project.

A party spokesman told the newspaper that Mrs May's announcement in October means there is "no need" to include it in the manifesto.

Sarah Olney, whose south-west London seat lies beneath the airport's flight path, responded to reports that an election pledge has been resisted by Foreign Secretary Boris Johnson and other Conservative critics.

She said: "Despite their earlier promises, the Conservatives are dead set on building a third runway at Heathrow.

"That would be disastrous for the environment; won't deliver the economic benefits the Government claim; and will be a blight on the lives of residents across south-west London.

"Failing to mention their commitment to expanding Heathrow in their manifesto won't fool anyone.

"It's clear that Conservative candidates in this election are standing on a platform of building a third runway at Heathrow."

Ms Olney unseated Zac Goldsmith as Richmond Park MP in December after he triggered a by-election by quitting the Conservative party in protest at its support for a third runway.

Mr Goldsmith was recently selected by the Tory party to stand in the seat again, although he said his stance on a third runway is unchanged.

The Lib Dems have consistently opposed Heathrow expansion, plans for which are currently under consultation.

A Conservative spokesman told The Sunday Telegraph: "There is no need for Heathrow to be in the manifesto because the decision was taken by the Government last year."