Hundreds of thousands more London residents would find themselves under new flight paths should Heathrow be expanded, a cross-party group of MPs and Lords has warned.

Senior Tories including Justine Greening and Boris Johnson joined Richmond MP Zac Goldsmith in the Commons on Wednesday to launch a campaign alerting people to the potential impact on neighbourhoods across the capital as the airports commission prepares to deliver its recommendation for a new runway at either Heathrow or Gatwick.

Flanked by a map depicting what he claimed would be newly overflown regions of the city – although Heathrow disputes it – Goldsmith said Heathrow was “already the biggest polluter in Europe by far” and that additional noise was just one of the reasons to oppose expansion. He said a third runway would mean “unmanageable congestion”, while the “economic case had entirely crumbled” and reinforcing Heathrow would see UK aviation “reverting to a taxpayer-funded monopoly”.

Johnson reminded the prime minister of his former unequivocal pledge to oppose Heathrow expansion, including a tree adopted by David Cameron on the site of the last planned third runway. He said: “I think that everybody remembers the manifesto that we ran on in 2010.

“It was a very clear campaign, it was the right campaign. I think the prime minister should stick with it. No ifs, no buts, no to a third runway, he said. He was right then and he would be right now.”

Although Johnson has promised to lie down in front of the bulldozers should a third runway be approved, he ruled out resigning as either an MP or from his increasingly intermittent role as mayor of London.

The senior Conservatives were joined by council leaders and MPs from constituencies neighbouring Heathrow - including Labour’s John McDonnell and Ruth Cadbury and Liberal Democrat Tom Brake. Green peer Jenny Jones said her party opposed expansion at either Heathrow or Gatwick, although several Tories, including the Windsor MP Adam Afriyie, urged building at Gatwick instead.

Goldsmith said: “We’ve been given a choice by the commission – that’s not one I’d set myself. I recognise by piling pressure against Heathrow expansion, I make it more likely that you have Gatwick expansion, but my first priority is to stop Heathrow expansion, it has to be.”

Johnson said: “We don’t think that Gatwick is optimal either.” But, he added: “The reality is that on any utilitarian calculus or environmental calculus of damage done to human life, Heathrow would be far, far the worse option.”

A Heathrow spokesperson said: “The map published today is inaccurate and unhelpful to local residents. The independent airports commission, made up of objective, technical experts has made its views clear – Heathrow expansion can take place while reducing the number of people impacted by noise.”

The commission, set up by Cameron in 2012 and chaired by Sir Howard Davies, is due to deliver a recommendation on whether Heathrow or Gatwick should be the preferred choice for the additional runway that it has already concluded Britain needs.