New Chancellor John Healey has given the Government’s full backing for a third runway at Heathrow.

Doubts had arisen over the plans to expand the west London airport as new Prime Minister Andy Burnham previously voiced concerns over it, warning it would divert investment funds from the regions.

The £49 billion project is also facing growing questions over its economic value.

At Treasury Questions in the Commons on Tuesday, Richmond Park Liberal Democrat MP Sarah Olney challenged Mr Healey over a third runway, slamming it as a “white elephant project”.

She stressed: “The Government's own appraisal report states that the net present value of expansion raises between minus £23.4 billion to minus £62.5 billion.

“So will this Chancellor put an end to this absurd proposal?”

But Mr Healey, MP for Rawmarsh and Conisbrough in South Yorkshire, threw his full support behind expanding the west London airport, as his predecessor Rachel Reeves had done.

He responded: “After years of delay, years of indecision, years of often vexatious challenge, we have given the go-ahead to this project quite simply because the economic case stacks up and will help bring growth.”

While Mr Healey’s position was crystal clear, other Cabinet ministers including Foreign Secretary Ed Miliband have previously raised objections to a third runway and its impact on global warming.

Airlines, including Sir Richard Branson’s Virgin Atlantic and British Airways owner International Airlines Group (IAG), have also heavily criticised the Government’s economic blueprint for a bigger Heathrow.

The warned that they and passengers face being left picking up a massive bill for a third runway which could spiral.

They are calling on the Government to impose a fifth test, on the development's affordability, alongside the existing four on its impact on climate change, noise, air quality and economic growth.

Heathrow wants another runway to increase capacity to 756,000 flights and 150 million passengers a year.

Transport Secretary Heidi Alexander sought to make the case for a bigger airport in west London in the draft Heathrow Expansion National Policy Statement (HENPS) published in the summer.

But IAG tore into the document and called for the total costs of the third runway scheme to be capped at £30 billion.

Virgin Atlantic stressed that the estimated £33 billion cost of a third runway, increasing to £49 billion once terminal area improvements and other investment are included, would be the "world's most expensive airport scheme ever constructed".

The project could also see years of travel chaos on the M25 as Heathrow’s plans include a £1.5 million scheme to move a section of the key motorway.

However, after Istanbul surpassed Heathrow as Europe’s busiest airport in July, the west London airport argued that “the case for expansion has never been clearer”.

It said another runway would "improve punctuality, reduce congestion and enhance the passenger experience", while increasing airline competition and "potentially saving" passengers £79 billion through lower fares over the next three decades.

But an authoritative new report warned just days ago that a third runway would “overshoot” the UK’s legally binding climate targets.

New modelling published by the University of Manchester’s Tyndall Centre for Climate Change Research, commissioned by environmental campaign group Friends of the Earth, said the UK aviation industry is already forecast to exceed legally binding limits in the seventh carbon budget, part of the national plan to reach net zero by 2050.

Research fellow Lois Pennington, from the Tyndall Centre, said: “Every aviation scenario the UK Government has published overshoots the carbon budget Parliament has legislated, before a third runway at Heathrow is even taken into account.”

Responding to the report, Lord Sadiq Khan said: “The truth is the whole case for Heathrow expansion relies on outdated evidence that fails to consider the urgent challenges we face today.

“I will continue to vehemently oppose these plans as I seek to build a fairer, safer, greener, more prosperous London for everyone.”