Protesters scale Parliament roof in anti-runway demo

Protesters calling for a halt to the expansion of Heathrow hold paper planes on Parliament's roof (AP)

Protesters sparked an embarrassing security alert at the House of Commons by staging a rooftop protest against the expansion of Heathrow airport.

Five members of the anti-aviation group Plane Crazy were arrested after gaining access to the roof of the Palace of Westminster where they unfurled banners attacking the plans for a third runway at the airport.

The protesters said they entered the palace as visitors, and walked on to the roof through an outside door, raising the prospect that a passholder helped them reach sensitive parts of the palace and guided them through the warren of corridors in the building.

Their protest was the second major security breach by environmentalists this week. On Monday, Greenpeace activists unfurled a banner on an airliner at Heathrow.

Yesterday's protest was the most serious breach of security at Westminster since pro-hunt activistsinvaded the Commons chamber in 2004 and comes after a significant tightening of security. It lasted almost three hours and ended shortly after Gordon Brown stood up in the Commons at the start of Prime Minister's Questions.

Mr Brown told MPs: "The message should go out today very clearly that decisions in this country should be made in the chamber of this House and not on the roof of this House.

"It is a very important message that should be sent out to those people who are protesting."

One of the rooftop protesters, Richard George, 27, from London, accused the Government of publishing a "fixed" consultation on the expansion of Heathrow. He said: "The aviation industry had taken full advantage of a weak prime minister to get the Heathrow consultation fixed.

"It does not even consider global warming despite everything Mr Brown has said about the environment and despite the massive impact aviation has on the climate."

The Labour left-winger John McDonnell, whose constituency includes Heathrow, said: "Direct action is an inevitable consequence of government refusing to listen to communities under threat and to the threat to our planet from climate change.

"No minister has visited my constituency to meet the people who will lose their homes and communities as a result of the proposed third runway.

"Ruth Kelly visited Heathrow to meet aviation businesses but has failed to visit the communities that are under threat of demolition. If politicians refuse to listen, direct action becomes inevitable."

A Department for Transport spokeswoman said yesterday: "The department has gone to great effort to encourage as many people as possible to participate in this consultation, by holding a series of public exhibitions supported by national advertising, posting summary documents to over 200,000 homes and making copies available from a dedicated phone number."