The Met Police is investigating black cab rapist over a new allegation of sexual assault as prison authorities prepare for his release

Scotland Yard is investigating a new sex attack claim made against black cab rapist John Worboys, it emerged today.

It is unclear whether the new investigation will affect Worboys' release, but it is thought that he could be kept in custody if the police investigation concludes quickly and new charges are brought.

Worboys was jailed indefinitely in 2009, with a minimum term of eight years, for drugging and sexually assaulting women passengers.

But a furious row erupted this month when it emerged he had been granted parole after serving his minimum term and will soon be released onto the streets.

Today it emerged a new claim, dating back to 1997, has been made to police in London, who have launched an investigation.

A spokesman said: 'The Metropolitan Police Service is investigating an allegation of non-recent sexual assault which was reported to police in January 2018.

'The incident is reported to have taken place in 1997. Enquiries by officers from the Child Abuse and Sexual Offences Command are ongoing.

'No arrests have been made. We will not give a running commentary on ongoing investigations.'

The Ministry of Justice would not comment when asked by MailOnline if the new investigation could halt Worboys release.

Worboys is thought to have many more victims than the 12 who he was convicted of attacking.

He gave women drugged champagne in his taxi after telling them he was celebrating

Worboys, now 60, was convicted of 19 offences against 12 victims, but has been linked to more than 100 complaints in total.

It was reported this morning that the notorious sex offender was transferred from HMP Wakefield in West Yorkshire to HMP Belmarsh, south-east London, at the weekend.

The news prompted fears he could be released in London, where he carried out his attacks and where many of his victims still live.

However, it is understood Worboys's release is not imminent and his transfer does not mean he will necessarily be freed into the capital.

Last week, Justice Secretary David Gauke stressed that Worboys will not be released until his licence conditions have been finalised, and victims signed up to a contact scheme have had their say on the restrictions.

Police found a rape kit in the back of Worboys' taxi which including sleeping tablets, condoms and an ashtray he used to crush the drugs

A group of MPs has called for an 'exclusion zone' to be imposed to ban the former taxi driver from the capital.

Richard Scorer, a lawyer at Slater and Gordon, which represented a number of Worboys' victims, said: 'This is extremely distressing for our clients as yet again they have not been informed about developments in the Worboys case.

'It is an insult that they have had to find out from the media of every new development in this case and it is crucial that they are kept updated.'

Mr Scorer told MailOnline when asked about the new probe: 'It would be inappropriate to comment while there is an ongoing investigation, but we would urge anyone with any information that may aid the criminal investigation to contact the police.'

Tory MP Zac Goldsmith said the proposed release of Worboys has 'absolutely horrified' his victims, who were 'appalled' to learn of his move to Belmarsh.

Daily Mail joins calls for Parole Board to say why it ruled attacker could be freed

The Daily Mail last night joined demands for the Parole Board to reveal its reasons for approving John Worboys for release.

Media groups, including the Mail's publisher Associated Newspapers, have sent a legal letter challenging officials to say why they ruled the black cab rapist can be freed. If the Parole Board refuses to disclose its reasons, the papers have warned they could bring a judicial review.

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. The letter states: 'The public has… been prevented from receiving factual information and opinion in respect of the Parole Board's decision. Such information is clearly integral to the debate on a matter of profound public interest.

'The Parole Board's failure to make public its decision is particularly significant in view of the overwhelming public concern that has been generated by the impending release of a person who was convicted of very serious crimes only eight years ago, and who is alleged to have committed many more… for which he has not been prosecuted.'