Lord Greville Janner of Braunstone, will not face charges over alleged historic child sex crimes. Alison Saunders, the director of public prosecutions, is due to announce today (16 April) that it is not in the public interest to put him on trial.
Crown Prosecution Service lawyers have spent nine months studying evidence gathered by Leicestershire police's Operation Enamel and detectives have interviewed more than 20 men who claim they were abused by Lord Janner, a former Labour MP for Leicester West, in their youth.
Police officers visited the alleged victims to inform them of the decision not to proceed to trial, The Times reported.
Lord Janner, 86, has always vehemently denied the allegations against him when they first surfaced two decades ago.
He has not been interviewed by detectives because of poor health, but police obtained warrants to search his home in Hampstead, north London and his office in the House of Lords.
He was previously investigated in the early 1990s, but detectives on the case were told by senior officers that they must not arrest the MP or search his property.
Ms Saunder's decision has angered campaigners who believe a trial would be in the public interest.
The National Association for People abused in Childhood said that the CPS decision was a "step backwards for justice".
Pete Saunders, a spokesman, told The Times: "There is enough evidence to proceed with this case and that Alison Saunders can say it is not in the public interest is an outrage."
Lord Janner, a prominent speaker on Jewish rights who was President of the Board of Deputies of British Jews - the umbrella organisation of the 300,000-strong British Jewish community - has been hailed for his efforts to see Holocaust victims receive compensation.