The Children's Society, which analysed the figures, claimed that police forces may be unaware of their duty under the Act to call in welfare agencies to help desperate young people picked up on the streets.
It said that schoolgirls who resort to selling their bodies to survive are being punished and labelled as prostitutes, rather than protected as victims of sexual abuse. Young people who are cautioned have a record for soliciting on police files.
Under the terms of the Act, the number of girls under 16 - the legal age of consent for sexual intercourse - who are cautioned should have fallen if police had followed the correct procedure and brought in welfare agencies. However, Home Office figures showed that in three of the 'top scoring' forces - West Yorkshire, Manchester and Cleveland - the number cautioned for soliciting had risen by 80 per cent.
Ian Sparks, director of the Children's Society, said: 'Young girls are being picked up by the police and cautioned for soliciting when many of them are not even old enough to consent to sex.
'If an adult had sex with a child in the home, residential care or school, it would be called sexual abuse and the perpetrator would be brought to book. But on the streets it is the young people who are punished.'