The Director of Public Prosecutions has been criticised for suggesting people who believe they have been raped but stay silent during their ordeal may give the impression they have consented to sex.
Alison Saunders said prosecutors considering rape cases must look at whether the suspect had a reasonable belief in consent.
But critics said it is common for rape victims to "freeze", finding themselves unable to move during an attack, and said the justice system is continuing to fail victims of sexual violence.
Ms Saunders told the Evening Standard: "So in some of the cases you can see why even though the complainant may think they were raped, there was a reasonable belief that they had consented, either through silence or through other actions or whatever.
"We are there not just to be able to prosecute cases where there has been an offence, but also not to prosecute cases where there isn't sufficient evidence."
In response to the comments Rape Crisis England & Wales said there is a "moral and legal responsibility to actively seek any sexual partner's consent".
The charity added: "Through more than 40 years' experience of providing frontline, specialist support to people whose lives have been impacted by sexual violence, we know it's common for victims and survivors to freeze or flop, finding themselves unable to speak, fight back or even move, and that knowledge is backed up by a large body of independent evidence, of which the Crown Prosecution Service (CPS) is aware."
Ms Saunders also described as "disappointing and irritating" the collapse of cases due to evidence not being disclosed as early as possible.
Surrey Police and Scotland Yard have announced reviews of their rape cases following the high-profile collapse of a number of trials, due to suspected flaws in investigations or concerns related to the disclosure of evidence.