Daniel Janner, a QC, said he had been told by a well-placed source that a strand of the £100 million inquiry into allegations his father was a paedophile and that the Establishment had covered it up was being dropped.

Mr Janner said: “A wholly reliable source has informed me the strand into my father is to be dropped.”

The Independent Inquiry into Child Sexual Abuse (IICSA) was plunged into crisis  with the resignation of Ben Emmerson QC, the counsel to the inquiry. Mr Emmerson quit the role on Thursday night, 24 hours after being suspended by IICSA. Mr Emmerson’s deputy, Elizabeth Prochaska, has also resigned while three chairmen have departed.

The inquiry is looking at 13 separate strands that could take a decade to complete. Two years after it was launched by Theresa May when she was Home Secretary, the inquiry is still to hear any evidence in public hearings.

The first of those – into claims Lord Janner sexually abused boys in children’s homes in Leicester where he was a Labour MP – were due to begin in the autumn but were postponed until March after police said inquiries were continuing.

More than 30 alleged victims were lining up to give evidence against Lord Janner, who died in December.

But his family have raised a series of objections, claiming that the inquiry is a “kangaroo court” which effectively plans to put on trial a dead man who cannot answer back. They also complain that the alleged victims cannot be cross-examined under its terms.

They have also argued that it is manifestly unfair because IICSA is supposed to be looking at institutional sexual abuse rather than the alleged activities of a single individual.

Lord Janner was never convicted of any crime although the Crown Prosecution Service has said there was enough evidence to charge him with child sex abuse. A court ruled he was unfit to stand trial because of his dementia.

When asked whether Daniel Janner was correct in claiming his father’s strand was to be dropped, Professor Jay replied: “All I can say is there is a review under way and it is not completed yet.”

A separate source at the inquiry, when asked whether the Janner strand was being dropped, said: “Maybe,” before adding: “We don’t plan to do anything other than what we are doing.”

Liz Dux, a lawyer representing several of Lord Janner’s alleged victims, said: “I would be appalled if any decision was made about that without any consultation with the core participants.”

She said they had not been told about any review. The alleged victims are suing the Janner estate for damages in a separate action.