Heathrow expansion plans under siege

Controversy continues over the proposed third runway at London's Heathrow airport, which the government is expected to approve this week, along with a sixth terminal. Yesterday, about 250 protesters in fancy dress camped and picnicked at the airport. Meanwhile, environmental group Greenpeace has bought a chunk of the land earmarked for the expansion, and is preparing for a legal battle to defend it.

There was speculation late yesterday that a decision could be delayed after prime minister Gordon Brown agreed to meet Labour Party backbenchers opposed to the project. The Conservatives and the Liberal Democrats both oppose the plans, as do dozens of environmental groups.

Greenpeace has bought a field the size of a football pitch and plans to invite protesters to dig networks of tunnels across it, similar to those built in the ultimately unsuccessful campaign against the Newbury bypass in 1996. The group also plans to divide the field into thousands of tiny plots, each with a separate owner. The British Airports Authority, the airport's owner, would be forced to negotiate with each owner, lengthening the 'compulsory purchase' process.

Emma Thompson, the actress, along with comedian Alastair McGowan and Zac Goldsmith, a Conservative adviser on the environment, were among those who signed the deeds to the site last Friday. They each contributed a small, undisclosed sum towards the purchase, but most of the £20,000 cost was met by a secret donor.

More than 40 lawmakers from the ruling Labour party, as well as London mayor Boris Johnson, a member of the Conservatives, oppose the proposals, arguing that there is no economic need for a third runway, and it will increase pollution. But business and trades union leaders believe the project is vital to the British economy, and would create at least 50,000 new jobs.

In an effort to mute criticism, the government is likely to attach several conditions to its approval of the Heathrow plans. The suggestion made by London First, a business lobby group, is likely to be implemented – it calls for a mechanism under which the number of take-off and landing slots at the expanded airport would be reduced automatically if the punctuality of an airline fell below a certain level.

Colin Matthews, chief executive of BAA, supported the idea of a target, but refused to say what level he believed it should be. It is likely that the number of flights at Heathrow will not be allowed to increase if that would result in air pollution and noise level norms being breached. The government is also considering setting a punctuality target for Heathrow that airlines would have to attain before they were granted additional runway slots.

Matthews told a London newspaper that the new runway and terminal would cost about £9 billion and would open in 2019 or 2020.

In yesterday's demonstration, organised by eco-activist group Climate Rush, the activists wore clothes in the style of the early 1900s – some dressed as suffragettes, others as chimney sweeps, with obvious historical resonances. With a string quartet playing in the background, they chatted, sang and sipped from champagne glasses.

A simultaneous protest attended by about 50 people took place at Manchester airport in northern England.