Gordon Brown’s plans to extend the 28-day limit on the time terrorist suspects can be held without charge were on Tuesday dealt another blow after MPs concluded that neither the government nor the police had made a convincing case to justify such a move.

A leaked draft of the Labour-dominated Commons home affairs committee says the terrorist threat facing the UK is “real, acute, and growing”, and therefore the call from the police – backed by ministers – for an extension of the maximum detention period must be treated with “great seriousness”.