Failures by police and prosecutors meant three chances were missed to charge Lord Greville Janner over sex abuse claims, an independent report has found.

Alleged victims of the late peer were left “devastated” after a criminal case was dropped on Friday, decades after they first accused him of abuse.

Today, a report by High Court judge Sir Richard Henriques found that in 1991, a decision not to charge the peer was wrong and there was enough evidence to charge him with indecent assault and buggery.

The charging decision was taken after an “inadequate” police investigation and should have been delayed.

In 2002, police failed to pass on further claims against the late politician to the Crown Prosecution Service.

In 2007, again there was sufficient evidence to prosecute Lord Janner for indecent assault and buggery.

The judge said Janner should have been arrested and interviewed and his home searched.

Director of Public Prosecutions Alison Saunders said: “The inquiry’s findings that mistakes were made confirms my view that failings in the past by prosecutors and police meant that proceedings were not brought.

“It is a matter of sincere regret that on three occasions, opportunities to put the allegations against Lord Janner before a jury were not taken.

“It is important that we understand the steps which led to these decisions not to prosecute, and ensure that no such mistakes can be made again.”

The peer died aged 87 last month, days after he was found unfit to stand trial after being charged with a string of sexual offences dating back to the 1960s against nine alleged victims, who were mostly under 16 at the time.

A special hearing known as a trial of the facts had been scheduled for this year, but last week the criminal case was formally dropped following Lord Janner’s death