An undercover policeman firebombed a department store to infiltrate a group of animal rights campaigners, MP Caroline Lucas yesterday claimed.

The Green Brighton Pavilion MP accused former Met special branch officer Bob Lambert of planting the bomb while posing as a member of the Animal Liberation Front (ALF).

The explosion caused £340,000 worth of damage at the Debenhams store in Harrow.

Dr Lucas was speaking at a meeting in Westminster Hall yesterday (June 13).

She was covered by Parliamentary privilege, which protects an MP from legal action for defamation for anything they say in the House of Commons.

Dr Lucas said she had seen a witness statement which claimed Mr Lambert – who went under the alias Bob Robinson – planted the device in the Debenhams store as he tried to prove his worth to the ALF.

Two activists – Geoff Sheppard and Andrew Clarke – were jailed for planting devices in the Luton and Romford stores following the attacks in the 1980s.

But the third activist involved in the attacks was never caught and it is now alleged by Sheppard that it was the undercover officer, Dr Lucas said.

She said Sheppard had only discovered Mr Lambert was undercover following the exposing of Mark Kennedy as a police officer who had infiltrated a group of environmental activists about to go on trial for attempting to take control of a power station.

Dr Lucas said Mr Lambert had already admitted he was involved in a covert operation which led to the imprisonment of Sheppard and Clarke.

Dr Lucas 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.

“This case raises new questions about the rules governing undercover police infiltrators and informers, particularly when it comes to those officers committing a crime – an area where the law is particularly grey.”

Dr Lucas is now calling for an independent inquiry into undercover policing.

Policing Minister Nick Herbert insisted that under the Regulation of Investigatory Powers Act 2000, which has since come into force, there are much tougher guidelines for police to follow.

He said: “Undercover operations are sometimes necessary to protect the public, to prevent or detect crime. I think we should commend the difficult and often dangerous job performed by our undercover officers.”