A detective at Scotland Yard's new rape investigation unit, Sapphire, has been suspended over claims of "irregularities" in 30 cases.
The detective constable is also under investigation for his dealings with a woman who died in an apparent suicide pact at Putney in south-west London.
It is alleged that the Kingston-upon-Thames-based officer fabricated letters to victims from the CPS.
He said that inquiries had been discontinued, it is alleged.
The officer had contact with one of the two women - referred to as Miss B - who died in Putney in September.
The Independent Police Complaints Commission (IPCC) said both women had made unrelated reports of harassment to the Metropolitan Police in the years before they died.
IPCC Commissioner for London Deborah Glass said: "Both women raised concerns about how the police handled their reports of harassment, and we are examining whether the officers involved did what would be reasonably expected of them.
"We are also carrying out a further investigation, looking into a number of other cases handled by the officer in Miss B's case."
Last year senior officers decided to bring regional sex crime units, known as Sapphire teams, under the umbrella of one central command.
The unit opened in September last year after several months of frenetic reorganisation work.