The Westminster strand of the Independent Inquiry into Child Sexual Abuse (IICSA) has been branded a “witch hunt against dead politicians”.
Former Cabinet ministers, party whips, peers and MPs will give evidence during the three weeks of public hearings.
The inquiry is looking at allegations of child sexual abuse and exploitation involving high-profile figures linked with Westminster.
But Daniel Janner QC, son of the late Labour peer Lord Janner, claimed allegations forming part of the probe are based on “tittle tattle, false rumours and dodgy dossiers”.
The Westminster strand is one of 13 being considered by the inquiry, which was set up in 2015 in the wake of the Savile scandal and amid allegations that a paedophile ring once operated in Westminster.
Allegations involving Lord Janner will be dealt with in a separate strand of the inquiry.
Speaking outside the inquiry’s London headquarters on Monday, ahead of the first of the Westminster strand’s hearings, Mr Janner said: “This beleaguered inquiry behind me has turned into a witch hunt against dead politicians, such as Sir Edward Heath, Lord Brittan and my late father, Lord Janner.
“It will unjustly trash their reputations.
“They cannot answer back from the grave.”
He said the inquiry will “give credence to false accusers, and undermine genuine victims”.
Mr Janner added: “It’s a massive, out-of-control waste of money, it’s a shameful disgrace, it’s contrary to the basic principles of British justice.
“Dead people of impeccable character will be presumed guilty.
“And I have to say it is also extremely upsetting for the families of those involved.”
Representatives of MI5, the Metropolitan Police and the Independent Office for Police Conduct will also be called as witnesses during this month’s hearings.
The probe will look into whether political parties turned a blind eye to allegations and if there were attempts to cover up abuse claims.
It will also examine whether there was a culture in Westminster of trying to shield people of public prominence from proper investigation.
The IICSA has stressed that allegations against people accused of wrongdoing during the hearing are not necessarily true.