Despite some staunch opposition, the British government announced Thursday that it has approved construction of a third runway at London's Heathrow Airport.

"Heathrow is the only hub airport, it's our most important international gateway, it connects us with the growth markets of the future — essential for every great trading nation," Transport Secretary Geoff Hoon told MPs.

Prime Minister Gordon Brown, speaking in Berlin before the official announcement in London, said the decision would help Britain's economy.

"It is always our desire to make sure that we protect the economic future of the country while at the same time meeting the very tough environmental conditions that we have set ourselves for noise and pollution and for climate change," he said.

But the plan faces fierce opposition from environmentalists and MPs, a number of them in Brown's own party.

Opponents say the addition of more than 200,000 flights a year would torpedo the government's plan to reduce carbon emissions by 80 per cent by 2050 and also violate European Union pollution and noise standards.

Conservative MP Theresa Villiers, the shadow transport secretary, told BBC Radio 4's Today that any government environmental promises would be shown "to not be worth the paper they are written on." She also vowed that her party would cancel the project if they won the next general election.

Paul Earnshaw, of Greenpeace, said Heathrow expansion must be stopped to fight climate change.

"The environmental impact is quite huge because aviation is the fastest growing emitter of carbon dioxide and other emissions such as nitrous oxide."

John Stewart, chairman of a group representing people who live near Heathrow, told the Associated Press Thursday that campaigners are still confident they can stop the runway. He said the group is consulting its lawyer to map a legal strategy.

"The plan fact remains that if [the governing Labour Party] loses the next general election, this expansion will not take place," he said, characterizing the government's support as "the last gasp of the dinosaurs."

With files from the Associated Press