British lawmakers on Friday urged the rejection of plans to build a new airport east of London on the River Thames and instead backed the expansion of Heathrow, already one of the world's busiest air hubs.
Parliament's Transport Committee warned that the Thames proposal, dubbed "Boris Island" after its biggest champion, London Mayor Boris Johnson, would be extremely expensive and could harm local wildlife.
Johnson, one of the most colourful figures in British politics and widely seen as a possible future rival for Prime Minister David Cameron's leadership of the Conservative Party, argues that a new four-runway airport east of London is the only way to take pressure off crowded Heathrow.
But MPs said in Friday's report that Johnson's plan could force the government to close Heathrow, which lies to the west of the capital.
They instead supported contentious plans to give Heathrow an extra runway, or possibly two, in order to boost Britain's strained airport capacity.
"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," said Louise Ellman, chairwoman of the Transport Committee.
"Evidence to our inquiry also showed a substantial potential impact on wildlife habitat in the Thames Estuary," she added.
The report also said that "a new hub airport will only be viable if Heathrow closes as a commercial airport."
It argues that "the larger a new airport, the more likely it is that existing airports will close as a consequence."
But the proposal to expand Heathrow faces opposition from local residents who say it would push noise to intolerable levels.
Heathrow has only two runways and is running close to full capacity.
Advocates of expanding the airport -- including its owners -- say it is losing out to rival European hubs, such as Amsterdam's six-runway Schiphol airport, in the battle to attract passengers.
But Johnson described MPs' support for the expansion of Heathrow as akin to making an obscene gesture at Londoners.
"By suggesting that Heathrow should double its runways from two to four, the committee is putting four fingers up to hundreds of thousands of Londoners," he said.
"London and the wider UK do need a hub airport that can operate 24 hours a day without constraint and the only place that is possible is to the east of London."