A poll carried out by the parenting website Mumsnet found that 83 per cent of women do not report being sexually assaulted to the police.
Mumsnet ran the poll as part of its We Believe You campaign, which aims to support victims of sexual assault by highlighting how women are reluctant to report the crime out for fear of not being believed.
The online poll of 1,600 users found that 10 per cent of those had been raped and 35 had been sexually assaulted.
Of those, 23 per cent reported having been sexually assaulted multiple times.
Katie Russell, of the Rape Crisis charity, said the survey "reflects what we know from decades of working directly with women, that rape and sexual violence is widespread".
She said: "The vast majority of survivors who contact Rape Crisis do not report it to the police. Despite improvements in police procedure, victims of sexual violence often lack confidence in the courts and legal system."
A Home Office spokesman said the government is investing £10.5m over the next three years in rape support centres across the UK.
He said. "Every victim should have full confidence that they will be treated with dignity and that any allegation will be investigated thoroughly."
A new campaign to raise awareness was launched last week, as part of the Home Office's Violence Against Women and Girls: Action Plan.
The campaign's website, This is ABUSE, will give teenagers a forum where they can discuss the subject and, hopefully, alleviate any fear about coming forward to report an attack.