Greenpeace campaigners have staged a protest inside the Cabinet Office against the government's alleged use of wood from rainforests for doors and windows.

Scotland Yard confirmed on Wednesday that around 40 campaigners had entered the building - before claiming it an "ancient forest crime scene" and capturing a door.

A total of 37 arrests were made.

They claimed that the wood came from African rainforests - which is against a promise by the prime minister that all wood would come from sustainable and legal sources.

"Nearly two years ago Tony Blair pledged to source all government timber from 'legal and sustainable' sources. Today's expose shows he's totally failed to turn his words into action," said campaigner John Sauven.

"Trashing African rain forests for the government's doors and windows threatens gorillas and chimps with extinction."

"Blair must act now to make good his promises to stop bullying ancient forest destruction and only use wood from environmentally friendly sources," he said.

A spokesman for the Cabinet Office insisted that all wood had come from legal sources.

"Our contract stipulates very clearly that all wood used in the renovation work must come from certifiable sustainable sources," he said.

At prime minister's questions, Tony Blair described the demonstration as "misconsidered."

A spokesman for the Timber Trade Federation accused Greenpeace of engaging in a "publicity stunt".

"Greenpeace ignore the complex reality on the ground in many supplier countries. The UK trade is committed to encouraging its suppliers - wherever they are - to source their timber from sustainable and legal sources," he said.