Scotland Yard is facing serious questions after the prosecution of a man charged with murder quietly collapsed following an investigation into alleged police corruption.

In a devastating new blow to the Metropolitan Police, it can be revealed that one of the reasons the Crown Prosecution Service (CPS) offered no evidence against Ali Tasci, charged with stabbing a man to death, was because prosecutors had belatedly discovered the case may have been tainted.

The initial investigation into the murder was led by an officer who rose to a senior rank in the Met – and who was later identified as corrupt in a secret police report. It is also understood that another corrupt officer not involved in the original investigation was present at the crime scene before anyone had called 999.

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The family of the victim, Selhouk Behdjet, had no idea that an inquiry into suspected corruption had any influence on the decision to drop the prosecution at the Old Bailey earlier this year until they were contacted by The Independent. Mr Tasci has always denied the charges. News that a murder inquiry may have been compromised and a prosecution was later dropped poses disturbing questions over the extent of wrongdoing inside the Met, and raises fresh concerns over whether Scotland Yard under its current Commissioner Sir Bernard Hogan-Howe is willing to confront corruption in its ranks.

The Behdjet case has echoes of the recent scandals surrounding two other high-profile murder cases, those of Stephen Lawrence and Daniel Morgan, where police corruption was said to have tainted the inquiries. The Morgan case remains unsolved.

Mr Tasci was charged with the murder of Mr Behdjet, a drug trafficker who was killed in his flat in north London in 1994.

It is understood he was killed over a drugs deal involving several kilogrammes of heroin. The murder remained unsolved for almost 20 years until a cold-case review by the Met identified new forensic evidence and led the CPS to charge Mr Tasci in 2012.

The review by a Scotland Yard murder squad also identified historical intelligence on police corruption related to the case, but the potential vulnerabilities were not shared with the CPS before prosecutors made the decision to charge Mr Tasci in 2012. The Met said it was “not aware” of this.

Mr Tasci, 51, was then held on remand for two years inside Belmarsh, a high-security prison in south-east London which houses the most dangerous offenders.

For reasons that are unclear, a new investigation by the Met’s Directorate of Professional Standards into the original 1994 inquiry began in 2013 – one year after Mr Tasci was charged and awaiting trial. The Scotland Yard inquiry found no evidence of police corruption. However, the CPS said the results of the investigation did in part contribute to the decision to offer no evidence against Mr Tasci at a pre-trial hearing at the Old Bailey in February.

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In a statement, the CPS said it wrote to the family “to explain the central reasons for offering no evidence” which included the fact that some “key witnesses” had subsequently died while others could no longer be relied upon.

Senior CPS sources said it also offered the family a meeting when it would have raised the investigation by the Met’s Directorate of Professional Standards if the offer had been accepted.

However, the daughter of Mr Behdjet, who lives with her elderly mother, says they have never received any correspondence from the CPS.

Layla Holliday, who was six months’ pregnant when she learnt of her father’s murder, said: “I was shocked when The Independent told me about this. The police told me it was for other reasons and I trusted what they were saying.

“You always hear of suspected corruption and cover-ups but you never think it would be this close to home.”

A CPS spokesman said the investigation by the Met’s anti-corruption command led prosecutors to “conclude that the integrity of the crime scene could not be guaranteed”. The Met said it was “not aware” of the crime scene’s alleged compromise.

Layla Holliday recalls one of the police officers identified by The Independent visiting her home a couple of weeks after her father’s murder. She said: “He was asking me where all my dad’s money was. It was an odd question and made me more suspicious as my dad’s flat was ransacked after he was killed and we thought the police had been going through things which didn’t really relate to the investigation. At the time we just assumed they were doing their job.”

A police source familiar with the case said: “This news will cause utter chaos inside the Met. You can’t mess about with murder – it is the most serious offence on the books. There has been a massive cover-up to protect the reputation of the police and the family have been misled.

“The Met claims other damaging cases like the murders of Stephen Lawrence and Daniel Morgan were all such a long time ago. Well, this prosecution collapsed in 2014 and the full reasons were suppressed.

“I am afraid there is a cancer at the heart of Scotland Yard that has never, ever been dealt with.”

Keith Vaz, chairman of the Home Affairs Select Committee, said: “It is unnerving to discover another case of potential corruption which may have destroyed a legitimate murder prosecution.

“It is clear that there may still be skeletons in the closet which, despite the Met’s claims to the contrary, are affecting justice today. It is vital that all possible corruption is exposed in order to wipe the slate clean – otherwise many more families may be left without the closure they deserve.

“I will be writing to Alison Saunders, the Director of Public Prosecutions, to understand just how many prosecution cases have been compromised by corruption.”

A senior detective on the Behdjet case was later named as a rogue police officer in Operation Tiberius, a secret Met file compiled eight years later, in 2002.

The report found organised crime syndicates could infiltrate Scotland Yard “at will”.

Operation Tiberius claims the officer involved in the Behdjet case also caused a separate prosecution to collapse in 1998 before he left the force.

The prosecution of the detective’s own informant for fraud was aborted after the officer was found to have had “unauthorised and undocumented contact” with the suspect.

Once he left the Met, the officer went on to become a successful businessman and employed his informant, according to Operation Tiberius.

His lawyer said that the “substance” of Operation Tiberius was “false”. He added: “The information which you have, certainly insofar as it relates to him, is misleading, inaccurate and untrue.”