One in every 14 adults in England and Wales was sexually abused as a child, according to the first research of its kind.
Some 11% of women and 3% of men - an average of 7% - said they were sexually assaulted during their childhood, according to the Crime Survey for England and Wales.
The findings of the annual survey also suggested that 567,000 females aged between 16 and 59, and 102,000 males in the same age bracket, suffered “sexual assault by rape or penetration” as minors.
The findings came after the Office for National Statistics (ONS) introduced new questions about childhood abuse in the survey for 2016, which was released on Thursday.
Javed Khan, the Barnardo’s chief executive, said: “The sheer scale of those who reported witnessing or being abused as children is utterly staggering. It is everyone’s responsibility to keep children safe.”
Apart from sexual abuse, 9% of adults who took part in the survey said they had suffered psychological abuse and 7% physical abuse. Some 8% said they had witnessed domestic violence or abuse at home.
Other than in physical abuse cases, women were “significantly” more likely to report they had been an abuse victim than men, the ONS report found.
While it found that 42% of victims suffered two or more forms of abuse, more than half of sex attack victims suffered no other form of abuse.
Those blamed for psychological or physical abuse were most likely to be the person’s parents.
However, rape and penetration attack survivors said the most likely attacker was a friend or acquaintance (30%) or other family member (26%).
Three in four victims of these assaults said they did not report what happened at the time. The most common reason given was “embarrassment or humiliation, or thinking that they would not be believed”, the report found.
For other types of sexual assault, victims said the most common perpetrator was a stranger (42%).
The age at which boys were most likely to be abused was 11 (42%), while it was 14 (33%) for girls.
The report said older people were more likely to report having been abused than younger people, adding: “It is difficult to determine whether this indicates a reduction in the prevalence of child abuse in more recent years or whether it is due to survivors being more willing to disclose past abuse the further in time they are away from the experience.”
An NSPCC spokeswoman said the report “confirms the horrifying fact that a vast number of adults were abused as children and that many told no-one about the ordeal they had suffered”.
She added: “Whilst it’s crucial that those who have suffered are heard and the perpetrators of these awful crimes are brought to justice, the authorities’ primary focus must be on identifying those who are enduring abuse right now, helping them rebuild their lives, and catching offenders to stop them from inflicting even more harm.”
Labour’s Sarah Champion called on the Government to take action, saying: “If we are to prevent another generation growing up with the consequences of widespread child abuse, we have to teach children how to protect themselves from abuse.
“My research with survivors, experts and charities all shows that compulsory age-appropriate resilience and relationships education for every child is the biggest single step we could take to prevent abuse, but this was reportedly blocked by David Cameron.”
Safeguarding minister Sarah Newton said: “This Government has done more than any other to lift the lid on non-recent child sexual abuse and ensure the mistakes of the past are not repeated, including establishing the Independent Inquiry into Child Sexual Abuse. We have also increased funding for violence against women and girls’ services to £80 million between now and 2020.”