Rape prevention work needs to be undertaken by police officers, not just community groups, one of the Met's top officers has said.
Dep Asst Commissioner Martin Hewitt told the BBC that police have only been "reactive", after an abuse has taken place, and says officers should focus on who are vulnerable, or in institutions, and could be potential victims.
Waiting for victims to report rape is not working, he suggested.
TOP STORIES OF THE DAY
"Most rape involves the coming together of some form of power and some type of vulnerability; either permanent or temporary," Hewitt said.
"We need to be utilising all our powers and tactics to understand how this happens, to mitigate the vulnerability and reduce the opportunities for that power to be abused."
Hewitt said victims needed to be made aware that more than a third of rape prosecutions did not end in a conviction, and that police needed to be "honest" about the challenges in securing a conviction.
"A lot of people feel that they will be questioned or they will be seen as being culpable.
"So the message that I want to give is you will be listened to, you will be believed, and that it is really important for people to report these offences so we understand how much of this crime is happening," he said.
Lisa Longstaff, from the campaign group Women Against Rape, told the BBC: "The real problem that women have is that they go to the police and report and the person is investigated and yet nothing's done.
"And even worse than that, too many of the cases are closed, people are being given cautions or they're just saying no further action."