Lawyers representing a group of people who claim they were sexually abused by the former Labour MP Lord Janner say they are to seek a review of the decision not to prosecute him.
The Director of Public Prosecutions announced Lord Janner, 86, would not be charged, despite sufficient evidence to bring a case, because of his dementia.
The ex-MP has denied any wrongdoing.
The CPS Victims’ Right to Review Scheme allows a complainant to request a charging decision be reconsidered.
Guidelines suggest a review, to be conducted by a prosecutor unconnected to the original case, would normally take six weeks.
Slater Gordon has confirmed it has written to the CPS on behalf of its clients, formally requesting a review, and one other law firm is understood to also be making an application.
The CPS has confirmed it has received at least one request for a review of its decision.
Announcing her decision on on 16 April, DPP Alison Saunders said there was enough evidence to prosecute Lord Janner for 22 offences against nine children.
But she said the CPS also has to decide if a prosecution is in the public interest. Four medical experts concluded Lord Janner was not healthy enough to enter a plea, instruct a solicitor or take part in a trial after he was diagnosed with Alzheimer’s in 2009.
BBC home affairs correspondent Tom Symonds says it is likely the review will centre on this medical assessment, along with the question of whether the DPP was wrong to rule out a so-called trial of the facts.
This would have involved a jury hearing details of the alleged abuse, and deciding whether it happened, without there being a possibility of Lord Janner entering a plea or facing conviction.
Ms Saunders decided such a trial should not take place because under law it could only result an order that Lord Janner be confined to hospital, a supervision order or an “absolute discharge”, a decision by the court that no further action should be taken.
She said Lord Janner was not a risk to the public because of his condition, and therefore it was not in the public interest to begin criminal proceedings.