A Labour MP has told how he urged Ed Miliband to kick Lord Janner out of the party last year after police told him of "stomach churning" abuse allegations against the peer.
Simon Danczuk said he wrote to the former leader last October - six months before the party took action - setting out how he had been visited by three senior officers from Leicestershire Police who were investigating serious allegations against the former MP.
The Rochdale MP said he called for Lord Janner to be suspended from the party at the earliest opportunity and criticised the party for being slow to act.
Labour suspended the peer in April when the Crown Prosecution Service announced he would not stand trial for historic sex abuse allegations because of the ''severity'' of his dementia.
Mr Dancuzk told Channel 4 News: "The nature of the allegations is so serious that really decisive action was required.
"All political parties have been slow to act in relation to child sexual abuse and allegations within political parties.
"It's also fair to say that the Labour Party isn't any different to the other political parties in failing to act quickly and efficiently on dealing with this sort of issue."
The CPS has said it will review its decision not to charge Lord Janner after a public outcry when it ruled out pursuing him.
He was accused of a string of offences during the 1960s, 1970s and 1980s but was deemed unfit to stand trial.
Justice Lowell Goddard, the New Zealand judge leading an independent inquiry into child sex abuse, said she would investigate claims against Lord Janner and could even call him to give evidence.
Greville Janner, 86, allegedly used his power as an MP for Leicester to abuse vulnerable young boys at a local children's home - claims he and his family strongly deny.
He was investigated by three different police inquiries between 1991 and 2007 and the CPS admitted this month it was wrong not to prosecute the peer back then.
A Labour Party spokesman said: "Any allegation of abuse should be taken seriously, and where crimes may have been committed it is rightly the job of the police to investigate them.
"When the Labour Party received notice of the allegations against Lord Janner, we asked Leicestershire Police to confirm that they were pursuing an investigation with a view to bringing charges, but they were unable to do so.
"As soon as evidence was produced by the Crown Prosecution Service, Lord Janner was suspended from the Labour Party.
"The victims of child sex exploitation need real support from the criminal justice system."