The study - Where is She Tonight? - found that of 827 prostitutes who used a drop-in centre funded by the social work department and local health board almost a quarter had become involved in prostitution by the age of 18. Four had begun at 13 and 68 by the time they were 16.

A multi-agency group involving social work and education, childcare agencies, the police and criminal justice is drawing up a protocol on child prostitution. Romey Langeland, social work head of children and family services, said: “If children under 16 are being prostitutes then this is an issue of child protection, not of criminality. These children are being abused by adults.”

Richard Barro, acting depute director of education, said that if teachers had concerns it was the school’s responsibility to act promptly and involve social work officers and the police. This had to be done “sensitively and in a way that the girl does not clam up and refuse to reveal information that could help her”.

The study found that 92 per cent of prostitutes had injected hard drugs. Neil MacKeganey, of Glasgow University’s Drugs Misuse Centre, warned: “A critical factor in terms of how people get involved in prostitution is making contact with someone already working in that area. If the young person makes that contact because of their drug-taking behaviour then they will be at risk.

“They will be shown how prostitution is a way of making substantial amounts of money that can then be used to feed their habit.”