Heathrow protesters scale British parliament roof

By Peter Apps and Jeremy Lovell

LONDON (Reuters) - Protesters scaled the roof of Britain's parliament in a major security breach on Wednesday and threatened further direct action against government plans to expand London's Heathrow airport.

Environmental protesters from the "Plane Stupid" group scaled the Houses of Parliament to mark the end of a public consultation period on a third runway and sixth terminal at what is already the world's busiest international airport.

"NO THIRD RUNWAY," read one of the banners they unfurled and hung down the side of the building.

The demonstration followed another serious breach on Monday when Greenpeace activists penetrated Heathrow's own security to climb on an aircraft and wrap a banner around its tail plane.

"This is all about no third runway," Plane Stupid spokesman Malcolm Carroll said. "The direct action movement know we have got to take these protests to another level to get the government to listen."

Security at parliament was beefed up after the September 11, 2001 attacks in the United States and tightened further when fathers' rights protesters hurled colored flour at then Prime Minister Tony Blair in May 2004 while he was in the debating chamber.

Britain sought to tighten security again at public buildings after suicide bombers killed 52 people in attacks on London's transport network in July 2005.

The government, business groups, airlines and airport owner British Airports Authority say Heathrow must either expand or risk losing out to continental rivals serving emerging destinations in India and China and damaging the economy.