Environmental group has bought piece of land earmarked for the airport extension as protest against development

Greenpeace has bought up a parcel of land earmarked for the construction of Heathrow's third runway in a bid to frustrate the development.

The environmental group has acquired land the size of half a football pitch near the village of Sipson - which could disappear by 2020 as part of the airport's expansion plans.

Those campaigning against the third runway have pledged not to sell the land to the government or airport operator BAA if the expansion goes ahead.

BAA, along with business and union leaders, have said the runway is vital for the British economy and supporters have said the scheme could create up to 65,000 jobs.

Greenpeace could sell off plots of land at home and abroad in order to force BAA to go through a lengthy court process to get access to the plots.

The move follows yesterday's pledge by London mayor Boris Johnson to launch a legal challenge if the government decides to press ahead with the runway. Recent planning legislation includes clauses that allow courts to consider whether or not a land purchase that blocked development was “vexatious or frivolous”.