Ministers have been urged to investigate claims that an undercover police officer who had infiltrated a group of animal rights extremists planted a fire bomb in a department store.

Caroline Lucas, the Green Party's leader, told MPs she had seen a witness statement alleging that Bob Lambert, who went under the alias of Bob Robinson – placed the device in a branch of Debenhams in Harrow, north-west London.

The device was one of three left by activists with the Animal Liberation Front to protest at its decision to sell fur products. Two ALF members, Geoff Sheppard and Andrew Clarke, were jailed for planting fire bombs in stores in Luton and Romford in 1987, but the third activist involved in the attacks was never caught.

Speaking under parliamentary privilege, Ms Lucas said Sheppard now alleged that Lambert had been responsible. Reading out part of Sheppard's statement, she said: "There's absolutely no doubt in my mind whatsoever that Bob Lambert placed the incendiary device at the Debenhams store in Harrow.

"I specifically remember him giving an explanation to me about how he had been able to place one of the devices in that store."

Ms Lucas, the MP for Brighton Pavilion, said: "It would seem that planting the third incendiary device was perhaps a move designed to bolster Lambert's credibility and reinforce the impression of a genuine and dedicated activist. He did go on to successfully gain the precise intelligence that led to the arrest of Sheppard and Clarke and without anybody suspecting that the tip-off came from him. But is this really the way we want our police officers to behave?"

Last night, Mr Lambert denied the claims. He told The Guardian: "It was necessary to create the false impression that I was a committed animal rights extremist to gain intelligence so as to disrupt serious criminal conspiracies.

"However, I did not commit serious crime such as 'planting an incendiary device at the [Debenhams] Harrow store'."

Belfast Telegraph