Serious doubts were raised about the financial viability of building a new hub airport in London today, after an influential committee of MPs said it would require an injection of taxpayer funds.
Research by the transport select committee found a new airport would not be commercially viable without support from the taxpayer.
"The results suggest a new airport would require public investment and have considerable impact on Heathrow and other London airports," chair Louise Ellman said.
Economic consultancy Oxera found significant investment would also be required to create the surface transport links needed to service a new airport.
The report will prompt new questions for the Davies Commission into aviation capacity in the south.
Boris Johnson is arguably the most prominent of campaigners for a new airport to be created, with the London mayor set on a Thames Estuary option.
The findings are unlikely to deter those opposed to expanding Heathrow, because they do not take into account social or environmental cost benefit analysis.
Most opponents of Heathrow expansion argue the airport forces planes over the city, causing noise and air pollution – a concern with associated costs which would not be incorporated into the Oxera report.
MPs were careful to stress today's announcement was just an initial finding in a long assessment process, but the need for taxpayer funds could weigh heavily on a future government as it tries to take a decision on aviation capacity amid increasingly painful spending cuts.