Joe Calzaghe was bullied when he was younger

Welsh boxing champion Joe Calzaghe has urged children who are being targeted by bullies to speak up about the problem.

Calzaghe, who suffered from bullying as a teenager, spoke out as a helpline charity revealed that more children asked for help about bullying than any other subject.

ChildLine Cymru/Wales - which is marking its 10th anniversary - also reported that bullies were increasingly using threatening text and e-mail messages.

Super-middleweight Calzaghe, 30, said he regretted bottling up the fact he was bullied.

"When you are a young child, the smallest thing can get under your skin and really upset you and affect your schoolwork because you can't concentrate," he said.

"Tell someone about it - don't be embarrassed," he added.

ChildLine Cymru/Wales said children are being threatened in the classroom and at home by bullies who have found out their victim's mobile telephone number or e-mail address.

One 14-year-old asthmatic girl called Karen was sent two messages reading: 'In five days you'll be dead' and: 'You must do what we say, wait for our next call'.

She was distressed by the messages and called ChildLine for help.

Another teenager whose mother had died of cancer was sent messages by a former best friend threatening to kill her.

Children's Commissioner for Wales Peter Clarke - who served as director of ChildLine Cymru/Wales for six years - said youngsters targeted by text and e-mails had no escape from bullies.

"Your mobile phone is something that becomes quite personal, you feel safe with it, but if bullies reach you on it, there is no hiding place.

Children are being targeted with text messages

"It is a problem we are aware of and it is high on our agenda," he added.

Mr Clarke said that schools had a legal role to deal with bullying.

ChildLine Cymru/Wales has helped more than 20,000 victims of bullying in the past 10 years through its helpline centres in Rhyl and Swansea.

It offers both Welsh and English language services.

A spokeswoman said that, if text bullying got really severe, police could block numbers.

ChildLine Cymru/Wales has also developed an outreach programme called Chips, which has been set up in schools who want to develop anti-bullying tactics.

So far, the charity has helped 150,000 children in Wales since it was set up in 1993, saving lives, protecting youngsters from abuse and found shelter for children on the streets.

The free UK-wide helpline service was set up in the 1980s, following an appeal on the BBC programme That's Life for viewers' help in conducting a survey on child abuse.

The helpline now receives more than 138,000 calls each year.