Lord Janner's family have been granted core participant status in the child sex abuse inquiry.
Daniel Janner QC, Rabbi Laura Janner-Klausner and Marion Janner applied to have a formal role in the investigation into institutional responses to allegations of sexual abuse involving their late father.
Chairwoman Professor Alexis Jay approved their request for core participant status on behalf of Lord Janner's estate on Tuesday, the Independent Inquiry into Child Sexual Abuse (IICSA) said.
Thirteen different investigative strands spanning several decades and examining a host of different institutions are being pursued by the inquiry.
Lord Janner, who died in December 2015, is alleged to have abused youngsters over a period spanning more than 30 years dating back to the 1950s.
His three children argue the existence of a strand examining allegations against Lord Janner - the only individual to be "singled out" - created an "assumption of guilt".
"Core participant status will finally enable our family to express our outrage that the inquiry has selected our innocent late father as a separate strand of his own, especially given that all the other strands are about institutions," they said in a statement.
"He is the only individual singled out which proves that the strand is based on a false assumption of guilt.
"Our late father lies silent in his grave and we are denied the right to cross-examine his accusers."
They added: "Having core participant status enables us to intensify our wholehearted opposition to an utterly disgraceful and unjust process and in no way represents a legitimising of the iniquitous strand."