Legal action has been threatened against the Parole Board by two newspapers if it does not disclose the reasons behind its decision to release black cab rapist John Worboys.
The Sun and Daily Mail wrote to the board and to Justice Secretary David Gauke giving them seven days to publish the confidential report.
Any refusal to grant the request would see lawyers launch a full judicial review application.
The latest development comes following news that Worboys, who was jailed indefinitely in 2009, has been moved from HMP Wakefield in West Yorkshire to HMP Belmarsh in south-east London ahead of his impeding release.
On Tuesday, police revealed they were investigating a fresh allegation of historical sexual assaultagainst the 60-year-old.
Announcing the newspapers' intentions, an article on The Sun website read: "The letter says the Parole Board's report is 'integral to the debate on a matter of profound public interest' where there is 'overwhelming public concern'.
"It warns the decision to keep the Worboys ruling secret is a breach of open justice and freedom of expression. And it concludes: 'We require that you publish the decision relating to Mr Worboys'."
The Daily Mail said on its site: "Rule 25 of Parole Board Rules state that information about decisions made on the release of prisoners 'must not be made public'.
"But the Mail and The Sun are arguing that such is the severity of the crimes for which he was convicted that the normal rules should be set aside."
Worboys has been serving a sentence for drugging and sexually assaulting women passengers.
He was convicted of 19 offences against 12 victims.
It is feared Worboys may have more than 100 victims and the Parole Board's decision sparked an outcry when it was made public earlier this month.
The Parole Board said it is legally prohibited from disclosing decisions or evidence.
A potential legal challenge by the Government over Worboys's release was ruled out by Mr Gauke last week, but lawyers for two victims have said they intend to pursue the case in the courts