A spat between the police and secret services escalated yesterday as the London Metropolitan Police confirmed it was investigating whether its case on MI6 complicity with torture was itself spied on.

The Met was forced to admit that its investigation into British intelligence services’ involvement in the rendition of Libyan rebels could have been compromised.

The discovery that MI6 had eavesdropped on lawyer-client communications linked to the case was first made by legal charity Reprieve.

Speaking on the new revelations US lawyer and Reprieve member Cori Crider said: “It seems blatantly obvious that those under investigation by the police for serious crimes should not have access to the details of that investigation.

“Yet that is just what we fear may have happened here.”

She added: “Not content with being able to skew trials in their favour by spying on lawyers, the government may now have gone as far as snooping on evidence that has gone to the detectives investigating the government in Operation Lydd.”

As previously reported in the Star, correspondence between former MI6 counter-terrorism unit head Mark Allen and Colonel Gadaffi’s Minister of Foreign Affairs Moussa Koussa was found in 2011.

It revealed that British personnel might have been involved in forcibly moving Abdel-hakim Belhaj, Sami al-Saadi, their wives and children from hiding and into Libyan prisons.

“The government needs urgently to explain whether the police investigation has been in any way compromised by their eavesdropping policies,” added Ms Crider.

“Ministers and officials must stop behaving as though they are above the law.”