Leading children's charity Barnardo's wants police and prosecuting authorities to pursue those who breach these laws, which came into force a year ago to ensure maximum protection for vulnerable teenagers. So far no prosecutions have been brought.
They issued the plea following the admission by Canadian supply teacher Amy Gehring - after she had been cleared of indecently assaulting Surrey schoolboys - that she did have sex with a schoolboy of 16.
The new law on abuse of trust was introduced as part of the Sexual Offences (Amendment) Act 2000.
The Act aims to protect children and young people in school, in local-authority care, or in custody who might be vulnerable to sexual exploitation by adults who are supposed to be caring for them.
Ms Gehring escaped prosecution under the Act because the accusations against her were made before the Act reached the statute book.
Barnardo's chief executive, Roger Singleton, said: "The admission by a 26-year-old teacher that she had a sex with a 16-year-old pupil highlights the need for this important new legislation.
"It also underlines the need for vigorous checking procedures for all staff working in positions of trust with children and young people, whether on a permanent or temporary basis.
"We are aware that the offences in the news took place before the Act was in force, but, so far, we are not aware of any prosecutions - or proposed prosecutions - under the new legislation.
"This seems an opportune moment to remind everyone that this extra protection for children now exists - and to encourage its use where a clear abuse of trust has taken place."
The legislation was introduced following a number of high-profile cases in which teachers had relationships with pupils. Previously, teachers who had sex with pupils in their care were not committing an offence as long as the pupil was over 16.