Four ex-police officers involved in the conviction of an innocent man who was jailed for 17 years for a rape he did not commit are now under investigation, watchdogs have said.

And one of the former officers is under criminal investigation for potential misconduct in a public office and perverting the course of justice, the Independent Office for Police Conduct (IOPC) said.

Andrew Malkinson, 58, was jailed for rape in 2004 until his conviction was quashed by the Court of Appeal last year.

The IOPC is now investigating complaints by Mr Malkinson about Greater Manchester Police (GMP) and its rape investigation leading to his jailing.

The IOPC said the four areas it is focusing on are whether police followed the appropriate processes during the identification of Mr Malkinson as a suspect, whether witnesses were offered any incentive to provide evidence, the alleged failure to disclose information that may have helped Mr Malkinson’s defence at his trial and the handling and disposal of items of evidence.

Catherine Bates, IOPC regional director, said: “Mr Malkinson is a victim of one of the worst miscarriages of justice in British history.

“We continue to work hard to ensure his complaints are thoroughly and independently investigated.

“Following a detailed review of evidence spanning a period of more than 20 years, we have now informed four retired GMP officers that they are under investigation for potential gross misconduct.

“One of the officers has also been notified that they are under criminal investigation for potential misconduct in public office and perverting the course of justice in relation to their actions during the police investigation and subsequent trial.

“Our investigation team continues to work hard to conclude our investigation as soon as reasonably possible, while ensuring our inquiries do not prejudice separate criminal matters linked to the crime Mr Malkinson was wrongly convicted of.

“We will continue to keep Mr Malkinson and GMP updated on our progress.”

The IOPC added that serving an officer with notice they are under investigation does not necessarily mean that disciplinary proceedings or criminal charges will follow.

At the end of its investigation, it will determine whether there is an indication that anyone serving with the police may have breached the standards of professional behaviour or if the case should be referred to the Crown Prosecution Service (CPS).

Toby Wilton, of Hickman & Rose, who is representing Mr Malkinson in relation to his police complaint, said: “Twenty years on from Mr Malkinson’s wrongful conviction no police officers have yet faced any sanction for their role in the miscarriage of justice that he suffered, Greater Manchester Police are yet to admit their responsibility for what happened, and he is yet to receive any compensation.

“This announcement that four officers involved will now face a misconduct investigation, and one will now face criminal investigation, is an important first step – but it is vital that all those responsible at Greater Manchester Police, as well as the wider force, are held to account.”

Mr Malkinson had his conviction quashed by the Court of Appeal in July last year.

He twice applied for his case to be referred for appeal by the Criminal Cases Review Commission (CCRC), but was turned down.

Mr Malkinson was eventually released from prison in December 2020.

Thousands of convictions are now being reviewed in the wake of his case.

The CCRC has been told to look back over all cases which have the “possibility of DNA opportunities”.

A review found delays and failings in Mr Malkinson’s case, spanning years, demonstrated a “deepseated, system-wide, cultural reluctance, which starts right at the top in the Court of Appeal, to acknowledge our criminal justice system will on occasion make mistakes, that entirely innocent defendants will sometimes be convicted”.

The CCRC admitted failing Mr Malkinson and offered an “unreserved apology.”