Parenting website Mumsnet has launched a campaign to support sex attack victims as one in 10 women responding to its poll said they had been raped.
The survey of 1,600 women by Mumsnet found a tenth of those who responded had been raped and a third had been sexually assaulted.
But more than four in five of the victims did not report the attack to police due to concerns over low conviction rates, embarrassment and shame, the figures showed.
A total of 1,609 women chose to complete the survey online between February and March.
Launching the group's We Believe You campaign, co-founder Justine Roberts said society was less sympathetic to victims than it should be.
"We simply shouldn't accept that we live in a country where one in 10 women are raped and over one third sexually assaulted," she said.
"Things are made worse by the feeling among many women that they can't talk about these crimes for fear of being treated unsympathetically, denying them access to practical and emotional support when they need it most.
"The message from the men and women on Mumsnet is clear: we believe you - and we want others in society to start believing you too."
Allison Saunders, Chief Crown Prosecutor for London, said: "I welcome this campaign by Mumsnet highlighting the extent of rape and sexual assault, and the obstacles that society puts in front of those who report them.
"Rape and sexual assault are dreadful crimes and ones that are often difficult for someone to report because of fear, shame and embarrassment.
"As the Mumsnet survey shows, victims can also be reticent to come forward for fear of being demonised in court and even in the media.
"I support the message of the We Believe You campaign, its aim to raise awareness of the extent of these crimes, and to challenge preconceptions."
The Crown Prosecution Service (CPS) welcomed the campaign, saying rape and sexual assault were dreadful crimes which were "often difficult for someone to report because of fear, shame and embarrassment".
Allison Saunders, the chief crown prosecutor for CPS London, said: "I support the message of the We Believe You campaign, its aim to raise awareness of the extent of these crimes, and to challenge preconceptions.
"As a society we need to be aware of the myths and stereotypes that members of the public who become jury members may hold and which have the potential to influence court outcomes and ultimately lives.
"We need to challenge these myths and stereotypes which prejudge victims and add to their ordeal."
She said prosecutors have done a lot of work to dispel the stereotypes and that the situation was improving.
Ms Saunders added: "I am determined to ensure that victims are confident in coming forward and reporting these crimes and I believe the MumsNet campaign will help us to achieve this."