The head of the Crown Prosecution Service will this week announce that she is standing down after the Government declined to extend her contract following a string of controversies.

Alison Saunders will end her term as Director of Public Prosecutions in the Autumn after five years amid intense criticism from Tory MPs and ministers following the collapse of a series of rape trials.

It comes as every rape case in the country is under review after the collapse of four rape trials in the space of two months when critical evidence was disclosed just days before cases were due to be heard in court.

A Whitehall source told The Telegraph: "It was felt a clean break was needed. Alison's tenure has been highly contentious, to say the least, and we want someone who can come into this job with a clear agenda. It was made clear that her contract would not be extended."

One senior lawyer said: "It has been a disastrous tenure, it has reduced the credibility of the role after Keir Starmer. I think that the respect for the profession of the role has been diminished."