The Metropolitan police is reviewing 63 sex-crime investigations dating back more than two years after a detective on its specialist rape-inquiry team was arrested over allegations of falsifying crime records.
A Detective Constable from the Sapphire sex-crime unit was held on suspicion of perverting the course of justice. Scotland Yard said it is trawling through his work records as there is "potential for unsafe convictions" although none has been identified.
The force said 27 live investigations handled by the detective had been given to new officers and 36 listed as completed were being reviewed. Charges had been laid in some cases. The cases related to investigations of rapes and serious sexual crimes in London's Camden and Islington. Two victims have so far been contacted by the force.
It is understood that none of the cases under investigation has been discontinued without proper investigation. The suspicion is that the officer may have cut corners or made decisions about whether anyone should be charged without proper consultation with prosecutors and senior officers.
"Any suggestion that an investigation is not up to the high standard expected will be fully investigated and any officers involved in potential failings dealt with robustly," Scotland Yard said in a statement.
The officer, who has not been named, was held in custody while two private addresses were searched. He was suspended in March while five cases were examined, but the police watchdog, the Independent Police Complaints Commission (IPCC), will take over the expanded inquiry after further "significant developments" came to light.
The inquiry comes a fortnight after the Crown Prosecution Service announced that a Sapphire detective, Ryan Farrow, would face 13 charges of misconduct over allegations he falsified police records dating back to 2007. He is due in court this month. The IPCC is also carrying out a wider review following complaints about Sapphire officers in the London borough of Southwark. None of the case are connected.
The Sapphire command has about 450 staff with 18 teams of specially trained officers in London. Jo Wood, of Rape Crisis England and Wales, said: "We will be watching very closely the outcome of this investigation."