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.