A law firm is expected to issue a judicial review claim this week over the Parole Board's decision to release serial sex attacker John Worboys - days after the lord chancellor dropped plans to challenge the release.

Harriet Wistrich, The Centre for Women's Justice

Harriet Wistrich, The Centre for Women's Justice

Birnberg Peirce sent a letter before claim to the Parole Board last week. The firm says the Parole Board rules are unlawful because they create a blanket policy preventing reasons for any decision being published. The decision to release Worboys 'in light of all the known facts surrounding his offence and reports of his progression in prison appears to be wholly irrational', the firm argues.

The Centre for Women's Justice, which is supporting the case, revealed today that it has raised £54,000 of a revised target of £100,000 through CrowdJustice, a crowdfunding platform, to probe why the Parole Board decided to release Worboys. A letter before claim was sent to the Parole Board last week. 

On Friday, justice secretary David Gauke told MPs that, after taking legal advice, it would be inappropriate to proceed with a judicial review. London mayor and former solicitor Sadiq Khan said the government's decision was 'astonishing' and announced he had instructed counsel on a possible judicial review. The Centre for Women's Justice says Gauke's decision does not weaken the charity's case.

A judicial review cannot automatically overturn the Parole Board's decision. If a court decides that the Parole Board's decision is unlawful, the decision will be referred back to the board.

Gauke has stressed that Worboys will not be released until his licence conditions have been finalised. Victims will have the opportunity to make representations on the conditions.

Gauke has decided to expand the government's transparency review to consider how Parole Board decisions can be challenged. Dame Glenys Stacey, HM chief inspector of probation, has been asked to conduct a 'rapid fact-finding exercise' to confirm whether legislative provisions and existing policy and processes were adequately followed. Her findings will inform a 'wider review'.

In a statement on Friday, the Parole Board said: 'We think this is a sensible course of action to take to make sure that the public and especially victims have confidence in the Parole Board's work.'