But on the opening day of his trial prosecutors were forced to offer no evidence when parliament torpedoed the case by insisting such matters were for it and not the criminal courts to decide.

The intervention, which came almost a year after Lord Hanningfield was first charged, means the criminal courts are virtually powerless to prosecute peers who abuse the very system that was introduced in an effort to clean up parliament.

Sources at the Crown Prosecution Service (CPS) last night expressed frustration and bafflement at the last minute decision.