Environmentalists are planning a campaign to halt the construction of a third runway at Heathrow airport in west London.

Campaigners have pledged to stop the project after it was disclosed that chancellor Gordon Brown intends to push ahead with the scheme.

Green groups had hoped, and the government had feared, that concerns over air pollution would halt the scheme.

But Brown’s pre-Budget report, published last November, said an upcoming study would aim to “identify solutions that would allow construction of a third runway to take place within air quality limits”. It also emphasised the airport’s “unique role in supporting economic growth across the country”.

Local groups, including Labour MP John McDonnell, whose Hayes and Harlington constituency is next to the airport, are now preparing themselves for a fight.

McDonnell accused the government and aviation industry of trying to “create an atmosphere of inevitability” about the expansion at Heathrow, but said they could not “get round the science of air pollution”.

He told The Observer: “They’ve underestimated the potential of an environmental campaign. My neighbouring Conservative MP, John Randall, has threatened to lie down in front of the bulldozers.”

The decision by Brown to persist with the Heathrow expansion comes as something of a surprise as a 2003 aviation white paper stated that the air pollution issue would delay the third runway by 10 to 15 years. In the wake of that, the government had backed the construction of a further runway at Stansted airport in Essex rather than the expansion of Heathrow.