French police had no grounds to detain Mohamed Merah, the self-proclaimed al-Qaeda extremist, before he went on a killing spree in Toulouse, according to Francois Fillon, the prime minister.

“There was no single element allowing to detain Mohamed Merah,” Mr Fillon told French radio. “We don’t have the right in a country like ours to permanently monitor without judicial authorisation someone who hasn’t committed an offence … We live in a state of law.”

Questions are being asked over how Merah, known to the authorities, managed to murder seven people, including three children, in three separate attacks, before being killed in a firefight after a 32 hour siege. . .