Jill Saward fears the proposal by Metropolitan Police Commissioner, Sir Bernard Hogan-Howe, will lead to alleged victims of rape not coming forward but instead "suffering in silence".
Britain's top police officer, Sir Bernard, has asked a former-judge to review how claims of historical abuse are investigated by Scotland Yard detectives.
His announcement comes after the Met's controversial Operation Midland, which handled claims of a paedophile ring in Westminster, allegedly involving well known figures.
Sir Bernard said officers should not believe alleged victims "unconditionally" but investigate allegations with an "open mind".
He added suspects should be offered anonymity before they are charged because "reputations may be tarnished" even before officers decide whether an allegation is credible.
Reacting to the announcement by Sir Bernard, Jill Saward said on Premier Christian Radio's News Hour programme: "For ...the head of the [Metropolitan] police to come on board and say that this must be the way forward is absolutely diabolical.
"The fact that he's singled out rape as a case where you don't necessarily have to believe somebody right from the word go, he hasn't done that for burglary, he hasn't done it for violence on the street, he hasn't done it for knife crime. He's casting doubt on victims and that is very, very damaging.
"One of the most difficult things for a victim to do is actually to make that decision to go forward and tell somebody that they've been raped. One of the things that people find over the years is that if they're disbelieved they won't tell anybody else. They'll suffer in silence."
You can listen to Jill Saward speaking with Premier Christian Radio's Alex Williams by clicking below.