Environmental campaigners were tonight camping on the roof of the Houses of Parliament in a protest about climate change.

Around 55 activists were believed to have perched on the Palace of Westminster after unfurling banners reading: “Change the politics, save the climate”.

Greenpeace said that at least 20 of the protesters were due to stay overnight. By midnight a total of 20 others, having lowered themselves to the ground, were arrested.

John Sauven, the charity's executive director, said the remaining protesters wanted to wait for the morning when MPs are due to return from their summer break, and urge them to sign up to a 12-point manifesto.

“We’ve got to raise the temperature of the debate because we are really running out of time. We are at a minute to midnight and there is so little time left but so much to do," he said.

“If we want to get people back to work and fill new industries that can be competitive and solve the problems of climate change, the political parties have got to get on message not just in tems of their words but also with their deeds."

After negotiating with police, some of the protesters began to descend a ladder down from the roof one by one just before 8pm. They were detained by police, dozens of whom had gathered on the pavement below including at least three dog handlers, and driven from the scene in the back of a police van.

A Metropolitan Police spokeswoman said: “Twenty people have been arrested for trespassing on a protected site. They are in custody at a central London police station."

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