A police inquiry into alleged murders by VIP paedophiles is in crisis as officers are no longer prepared to say that the key witness is ‘credible and true’.

An internal investigation has been launched into the running of the £1million Operation Midland inquiry after police found no evidence that a string of senior Establishment figures were responsible for killing three boys in the 1970s and 1980s.

In an extraordinary volte-face, Scotland Yard will not now say publicly that it still believes the account of the VIP murders by the ‘main witness’ – known only as ‘Nick’.

Named: Former home secretary Lord Brittan (left) and former prime minister Sir Edward Heath (right). Last night the Metropolitan Police suggested for the first time that the future of Operation Midland could be in doubt

Police plan to outline a new approach to the case as early as next week. This is likely to lead to the murder investigation being scaled down.

Last night the Metropolitan Police suggested for the first time that the future of Operation Midland could be in doubt.

It said: ‘An internal review of Operation Midland was commissioned on 8 April 2015. It is routine for investigations of this nature to be reviewed. The review was carried out with the full report submitted on 25 August.

‘The product of this review is under consideration. We are not prepared to comment on the review in any detail as Midland is an ongoing investigation.’

Sceptics suggested the Met is preparing an exit strategy for the inquiry, which has seen the homes of D-Day hero Lord Bramall and former Tory MP Harvey Proctor, also a suspect, raided by detectives and the pair interviewed under caution.

If, as expected, no charges are brought, Yard chiefs are expected to be dragged before a parliamentary committee to answer allegations of pursuing a witch-hunt.

Location: Operation Midland started nearly a year ago after a ‘main witness’ - known only as ‘Nick’ - claimed he was abused by a murderous paedophile gang linked to the Dolphin Square apartment complex (pictured)

Operation Midland started nearly a year ago after Nick, 47, claimed he was abused by a murderous paedophile gang linked to the luxury Dolphin Square apartment complex including former armed forces head Lord Bramall, former prime minister Sir Edward Heath, ex-home secretary Lord Brittan and former heads of MI5 and MI6.

The presumption of innocence before conviction is mislaid and any sense that the court should stand above the public pillory is regarded as quaint and historic Lord Macdonald, former director of public prosecutions

Nick claims he was abused at depraved sex ‘parties’ from the age of seven, and claims he witnessed horrific acts at Dolphin Square – which is near Parliament and is popular with politicians and Establishment figures – between 1975 and 1984. He claimed three boys were murdered.

Last December, weeks after the inquiry was launched, Detective Superintendent Kenny McDonald, said his officers believed Nick to be a ‘credible and true’ witness.

Critics now say it was ridiculous for the senior Met officer to make such an assertion, before police had tested Nick’s account – let alone gathered any evidence.

Asked yesterday whether his bosses supported his view, the Met pointedly dodged the question.

It said: ‘It is the role of the police to investigate, gather evidence and present that evidence to the Crown Prosecution Service to be considered.

Scotland Yard: Police plan to outline a new approach to the case as early as next week. Last night the Met suggested for the first time that the future of Operation Midland could be in doubt

‘If a case is put before the courts it is ultimately up to a jury to make decisions based on the evidence presented to them.’

Sir Bernard Hogan-Howe: A former senior Met officer predicted the case would cause ‘enormous reputational damage’ to the force and its boss

Since Mr McDonald spoke out, detectives have found nothing to support Nick’s extraordinary allegations of ritualistic killings involving the top tier of the security establishment.

As revealed in the Mail earlier this month, they have no idea who, if anyone, was killed, have found no bodies, have found no forensic evidence and have no reliable witnesses to back up the testimony of the main accuser.

One former senior Met officer predicted the case would cause ‘enormous reputational damage’ to the force and its boss, Sir Bernard Hogan-Howe.

The doubts over the future of Operation Midland emerged as the Daily Mail yesterday published an excoriating critique of the police’s child abuse inquiries by former director of public prosecutions Lord Macdonald.

‘In this frankly disturbing climate, long-standing British traditions of justice have been cast aside,’ he wrote.

‘The presumption of innocence before conviction is mislaid and any sense that the court should stand above the public pillory is regarded as quaint and historic.’

Earlier this week, it emerged that police had abandoned an inquiry into claims by one of the most outspoken ‘victims’ of the VIP child sex abuse scandal.

The man, known only as ‘Darren’, said he was forced to attend sadistic sex parties at the Dolphin Square complex. He said a girl may have been killed and named Lord Brittan as one of his abusers.