A 14-year-old boy was travelling home from school on a packed bus when he was approached by a gang of 15-year-olds. They had already taken phones, cash and iPods from five other pupils and he knew they were about to confront him too.

"He was on the bus in Southgate coming home it was broad daylight," said the victim's father, Lionel Pereira, of Oxford Avenue, Southgate.

"When he refused to give them his valuables, they punched him in the face. He came home with blood everywhere."

Soon afterwards the gang worked their way to a 12-year-old boy. "They split up and three of them came for me," said the pupil. "I told them to get their hands out of my pockets but they took my phone."

It was about 4pm a time when youth crime soars in the borough. It was a busy bus route home, yet crimes like this remain an everyday occurrence.

According to Barnet police figures, more than half of all robberies committed in the borough take place when pupils are going to and from school. And two-thirds of all street robberies since last April have involved the theft of expensive electronic equipment mainly mobile phones and MP3 players, such as iPods.

Last year, there were 4,001 crimes in the borough in which the accused was aged between ten and 18.

Barnet Action 4 Youth, a nationally-funded project run by crime reduction organisation Crime Concern, has reported that a staggering 69 per cent of youth-on-youth' crime in the borough involves some degree of violence.

So why do youngsters commit these crimes?

Dr Peter Kennison, a criminologist at Middlesex University, said: "Why does someone do anything? Opportunism, boredom, society's pressures on young people to achieve, the availability of property there are lists of reasons.

"They steal mobiles phones because they are small and easy to dispose of, and some young people see them as a fashion accessory. Wanting the latest phone around, a bit like wanting Nike trainers, they succumb to peer pressure."

Police in the borough said they did not know what happened to all the mobile phones that were stolen.

But Dr Kennison suggested: "Some of them take them and throw them away it's about control of people. Others take out the components, like the chips, and sell them on or sell them on to a middle person. It's a quick way of making money."

But he continued: "I would add, though, that we should not demonise young people there are very few prolific young offenders."

This is a view shared by Barnet Action 4 Youth, which works with people aged from 11 to 21 to prevent crime before it happens'.

The scheme involves discussion groups and activities to prevent youths from hanging around on the streets during school holidays. It aims to improve school attendance and also runs anger-management classes to help diffuse potentially volatile situations.

Project manager Alison Kira said: "We run projects in and out of schools to tackle issues that are important to them.

"Issues coming out more recently include carrying knives for protection this is an issue that we certainly weren't talking about 18 months ago.

"Three years ago the major issue talked about was phone theft. Two years ago the issue was gangs and this year it seems to be knives."

Young people carrying knives has become such a hot topic that the group has been given Home Office cash to specifically tackle the problem.

"We secured funding last week to show young people the alternatives to carrying knives for protection; things such as self-defence classes and de-escalation techniques that will be taught by a bouncer," said Ms Kira.

She pointed out that although a fear of crime apparently drives some youngsters to carry a knife, only six per cent of all recorded crimes in the borough over the last two years involved youth victims.

Youngsters can discuss their concerns about crime with police officers at regular informal meetings organised by Barnet Action 4 Youth. The fortnightly gatherings, known as CRAC (Communication, Results, Action Committee), take place on Tuesdays at Starbucks in High Road, North Finchley, from 5pm to 6.30pm. The next meeting is on March 7. For more information call 020 8205 8341.