A tiny proportion of sexual offences committed in England and Wales lead to a conviction in court, the first statistical review of its kind revealed on Friday.
Around 473,000 adult men and women are victims of a sexual offence on average each year, a joint overview by the Ministry of Justice (MoJ), Home Office and Office for National Statistics (ONS) estimated.
But only 54,000 sexual offences are recorded by police on average each year and 5,620 offenders are convicted, the review said, meaning around 1.18% of offences end in a conviction.
The report brings together, for the first time, a range of official figures from across the criminal justice system to provide an overview of sexual offending in England and Wales.
The review showed that one in five women has been a victim of a sexual offence, which includes the most serious crimes such as rape and other offences such as flashing.
Around 69,000 women are estimated to have been raped in the last year, while 90% of victims knew the perpetrator.
The study showed that just 15% of women reported the offence to the police, with the most common reasons for not coming forward being "embarrassing", "didn't think the police could do much to help", "too trivial" and "private matter".
Some 9,900 sex offences went to court in 2011 with 1,600 offenders found guilty at magistrates' courts and 4,400 convicted at crown courts.
There were just under 1,200 convictions for rape in 2011, compared with just under 800 in 2005, the figures showed.
There were also 19 cautions administered for rape, with 16 going to offenders aged 17 or younger.
The panel of experts behind the study said it was not possible to calculate a precise percentage figure to reflect the number of offences committed that lead to convictions because many of the statistics were not directly comparable.
But the team agreed the proportion of offences leading to conviction was "small".
The study also showed that it took up to 496 days to finish a case - from the day a sex offence is committed to when it was resolved in court.
The majority of this time - 295 days - falls between the date of the offence and the date the defendant is charged.
Holly Dustin, director of the End Violence Against Women Coalition, said there was "clearly a long way to go in improving the criminal justice system's response to these serious crimes."
"But we also have to look beyond the criminal justice system to ensuring that there is proper funding to support women and girls who experience sexual violence, whether or not they report to the police, and that health and other services get better at responding to this problem."
Deputy assistant commissioner Martin Hewitt, lead on adult sex offending at the Association of Chief Police Officers (Acpo) said: "In recent years the service has been working hard to improve our response in this area, including improving our recording and reporting practices and working with other partner agencies, including health, to encourage victims of sexual offences to come forward and report offences."
Yvette Cooper MP, Shadow Home Secretary & Minister for Women & Equalities, said the "dreadful" figures showed "national action is desperately needed to tackle sexual violence."
"It is appalling that the number of offenders being convicted for some of the most serious crimes is so low in comparison to the number of offences.
"And it is deeply unfair that so many victims do not get the justice or protection they deserve. More action is needed by the government, police, prosecutors, courts, councils and communities to deal with these horrible crimes and keep people safe."