Projects that use shock tactics to try to scare delinquents into improving their behaviour, as well as initiatives designed to raise the self-esteem of bullies, could be counter-productive, said Dr Manual Eisner, a Cambridge University criminologist.

He told a meeting of teachers, social workers and civil servants from across Europe that there was little or no proof that the hundreds of new projects being set up would be effective.

Citing evidence from the United States, which showed that only 12 out of 400 projects aimed at tackling youth violence could be proven to work, Dr Eisner said that the situation in Europe was probably even worse.

Speaking to The TES after his main address to the Council of Europe meeting in Strasbourg, Dr Eisner cast doubt on the value of a programme called “scare straight”, which developed in the US in the Eighties. “It involved going with kids to police stations and prisons and so on, with the intention of making them scared to commit violent acts,” he said.

“I cannot see any reason why this should have any positive impact. It creates a climate of threat and violence that these kids will not react well to, rather than building the positive emotional bonds with teachers and parents that are needed.

“There are also quite a few programmes that try to improve the self-esteem of violent youngsters, but there is good evidence that low self-esteem is not a problem they suffer from.

“In fact, bullies tend to be quite dominant people. They often have a degree of control over other kids and that’s a source of self-esteem. So if you boost their self-esteem even further I would not be surprised if you made the problem worse.”

Teachers and politicians in Europe should use approaches that had been tested and found effective so they knew they were using their time and money sensibly, he added.