London's Heathrow Airport, Europe's busiest, should be expanded with the addition of a third and even a fourth runway, a cross-party panel of British lawmakers said.
The alternative construction of a new hub airport to the east of the UK capital, as championed by London Mayor Boris Johnson, would not be commercially viable without "significant" taxpayer funding and should be rejected, the House of Commons Transport Committee said in a report.
"Heathrow, the UK's only hub airport, has been short of capacity for a decade and is currently operating at full capacity," Committee chairwoman Louise Ellman, a member of the opposition Labour Party, said in an e-mailed statement.
"We conclude that a third runway at Heathrow is necessary, but also suggest that a four-runway proposal may have merit."
Britain's airport capacity is currently being reviewed by a commission set up by Prime Minister David Cameron to put off a decision on expanding Heathrow until after the 2015 general election.
The panel will produce an interim report later this year.
Heathrow uses 99 percent of its runway capacity.
Cameron's Conservative Party made blocking the expansion of Heathrow a key pledge in its 2010 general-election campaign in a bid to win votes in west London, under the Heathrow flight path. It promised to make Heathrow "better, not bigger", stop the construction of a third runway and instead link the airport into Britain's proposed high-speed rail network.
Trying to create a split-hub system by developing rail links between existing airports is unviable, the panel, which has no London lawmakers among its members, said. It also argued for dedicated rail lines to be built to improve access to Gatwick Airport, south of the capital, and Stansted to the northeast. Connections to Heathrow should also be improved, it said.
The building of a third runway at Heathrow was proposed by Tony Blair's Labour government in 2003, subject to environmental standards. It became mired in legal, political and environmental arguments and was cancelled when Cameron's coalition government took over in May 2010.
The building of a new hub to the east of London, a proposal dubbed "Boris Island", should be rejected because it would lead to the closing of Heathrow and have "unacceptable" consequences for people and businesses in west London, the panel said.
The proposal would also need too much public money and would have a substantial impact on wildlife in the Thames Estuary, the committee said.