Plans for a new airport in the Thames Estuary should be rejected and Heathrow expanded instead, a report by MPs has said.
The House of Commons Transport Committee warned that a multi-billion pound hub east of London - favoured by Mayor Boris Johnson and dubbed "Boris Island" - would be prohibitively expensive.
A new airport would also damage wildlife in the estuary and mean the closure of Heathrow, a course of action that would have "unacceptable consequences", the report said.
The committee's findings will come as a huge blow to Johnson, who has long campaigned for a new London airport east of the capital.
Instead, the report states that a third runway at Heathrow is "necessary" and that a fourth runway could also be a viable option.
But expansion at Heathrow is opposed by local residents.
Louise Ellman, chair of the committee, said: "Research we commissioned made plain that building an entirely new hub airport east of London could not be done without huge public investment in new ground transport infrastructure. Evidence to our inquiry also showed a substantial potential impact on wildlife habitat in the Thames estuary.
“The viability of an estuary hub airport would also require the closure of Heathrow – a course of action that would have unacceptable consequences for individuals, businesses in the vicinity of the existing airport and the local economy.
“Heathrow – the UK's only hub airport – has been short of capacity for a decade and is currently operating at full capacity. We conclude that a third runway at Heathrow is necessary, but also suggest that a four-runway proposal may have merit, especially if expanding to locate two new runways westwards from the current site could curb the noise experienced by people affected under the flight path."
However, the report added that adding new runways to expand other existing airports is not a long-term solution.
For more information, visit parliament.uk.
To take part in the debate on Business Traveller’s forum on a possible airport in the Thames estuary, click here.
Report by Graham Smith