Criticism over England sex offence cautions
At least 1,570 people were cautioned for sex offences across England in the past year, the BBC has learned.
Police can use cautions instead of court action if people admit offences.
Justice Secretary Chris Grayling said on Sunday he would overhaul the system so serious offenders would no longer receive a "slap on the wrist".
But the Association of Chief Police Officers (ACPO) said cautions were carefully considered in "the vast majority of cases".
Magistrates' Association chairman John Fassenfelt said he believed the system was "failing" and police should not be involved in "sentencing".
BBC Inside Out asked 38 police forces in England for the nature of offences where officers had issued offenders with cautions in the year 2012-2013.
The figures showed at least 1,570 people had received cautions for sex offences.
These ranged from exposure and voyeurism at the lower end of the offending and custody spectrum to making indecent images of children and sexual assaults on children under the age of 13.
Mr Fassenfelt said it was the view of the Magistrates' Association that "that indictable crimes, serious crimes like sexual offences should virtually never be cautioned".
"We're worried that this trend will continue to increase and we end up with the police being people who catch them, people who prosecute and people who sentence - and sentencing is the responsibility of the judiciary."
In the Surrey force two officers are facing misconduct proceedings after an abuser was given a caution.
The victim was 34-year-old Lina Barnes, who was abused when she was nine years old.
She decided to speak out when she discovered her abuser had only received a caution.
"The amount of emotional turmoil that I'd gone through to actually report it to the police and take that big stand in doing so and then to be told he'd get a caution was very disappointing," she said.
Ms Barnes, a mother-of-one from Corby in Northamptonshire, said she felt "deflated" and "devastated" when she was informed of the outcome of her case.
Her offender's age - a man currently in his 70s - and the historic nature of the offences, were cited as reasons to issue the man with a caution.
ACPO spokesman Christopher Eyre, the chief constable of Nottinghamshire, said he had to accept there would be mistakes but the figures for those receiving cautions for sexual offences should be put into context.
He said: "In the vast majority of cases they're carefully considered and the caution that's applied is done in an informed way to achieve the right outcome both for the victim and against the offender."