A fifth of women in England and Wales have suffered a sexual assault, according to official figures.
More than three million females are estimated to have been victims of offences including rape, indecent exposure or unwanted touching.
The numbers were contained in a detailed analysis of data for the year to March 2017 by the Office for National Statistics (ONS).
It said the Crime Survey for England and Wales (CSEW) estimated that 20% of women and 4% of men have experienced some type of sexual assault since the age of 16, equivalent to 3.4 million female victims and 631,000 male victims.
An estimated 3.1% of women (510,000) and 0.8% of men (138,000) aged 16 to 59 reported that they had experienced a sexual assault in the last year. These percentages showed no significant change from the previous year's survey.
Sexual assaults measured by the CSEW cover rape or assault by penetration, including attempted attacks, as well as indecent exposure or unwanted touching.
The report said: "The year ending March 2017 Crime Survey for England and Wales estimated that 12.1% of adults aged 16 to 59 have experienced sexual assault (including attempts) since the age of 16, equivalent to an estimated 4 million victims."
Indecent exposure or unwanted sexual touching (11.5% of adults aged 16 to 59, 3.8 million victims) was more common than rape or assault by penetration, (3.4%, 1.1 million victims).
Respondents who said they had been victims of rape or assault by penetration since they were 16 were asked whether they thought the offender was under the influence of alcohol or drugs, and whether they were under the influence of alcohol or drugs themselves at the time of the incident.
In the most recent rape or assault by penetration, including attempts, 38% of victims reported that the perpetrator was under the influence of alcohol.
The same proportion of victims (38%) said they were under the influence of alcohol themselves.
Fewer victims reported that the offender was under the influence of drugs (8%) and that they were under the influence of drugs they had chosen to take (2%).
The report said more victims were under the influence of alcohol when the offender was a stranger (65%) compared with when the offender was a partner or ex-partner (19%).
Papers on the nature of violent crime and domestic abuse were also released on Thursday.
There were approximately 1.2 million violent crime incidents in the year to March, according to the crime survey. This figure showed no statistical change from the previous year.
An estimated 26% of women and 15% of men aged 16 to 59 had experienced some form of domestic abuse since the age of 16.
ONS statistician John Flatley said: "The data we've published today show the complexity of measuring crime in all its different forms. Even offences under the heading of 'violence' vary enormously, from minor assaults such as pushing and shoving to homicide."