The son of the late peer Greville Janner has vowed to bring a private prosecution against the man at the centre of Westminster child abuse claims, who has himself been charged with paedophile offences.

The accuser, who has been named only as Nick, sparked Operation Midland after he told police he had been raped and abused for nine years by a VIP gang.

The investigation, which cost more than £2m, collapsed without any arrests and Nick has appeared in court charged with possession of indecent images of children, to which he pleaded not guilty.

Last September Northumbria police said they had passed a file to the Crown Prosecution Service to decide whether charges of perverting the course of justice and fraud would be brought against Nick.

The former MP Lord Janner was among those accused by Nick of child abuse. Janner died in 2015. His son, Daniel Janner, has criticised the CPS for the delay in making a decision on charging Nick.

“Nick accused my late father of raping him – he must now be prosecuted for his lies,” he said. “If the CPS refuse, I will bring a private prosecution. The child abuse inquiry must now drop the strand in my innocent late father’s name, all the civil abuse claims against him having been dropped.”

Nick’s claims centred on a number of establishment figures, including the late Leon Brittan, a former home secretary; Lord Bramall, a former head of the armed forces; and the former Tory MP Harvey Proctor.

In November 2016 a scathing report from the retired judge Sir Richard Henriques said senior detectives had fallen for Nick’s “false allegations” and had misled a judge to obtain warrants to search the homes of innocent members of the establishment.

“He [Nick] associated Lord Janner with the group who physically and sexually assaulted and raped him,” Daniel Janner said. “I’m concerned, my father was named by Nick so I’m going to prosecute him if the CPS don’t. This delay is totally wrong, it’s extraordinary and smacks of a cover-up.”

Proctor has called for an independent inquiry into the anonymity given to alleged victims of sexual abuse.

“I have now come to the conclusion that the whole question of anonymity needs a complete review, investigation and overhaul,” he said. “I believe the home secretary, if not the prime minister, should set up an independent inquiry into the issue of anonymity. We can’t rely upon the police to police themselves on this matter.”

Nick faces six charges, including making indecent images of children, all of which he has denied.