Cyber-bullying, online and in text messages, is becoming a serious problem, so people working closely with those affected. Yuriko Nakao / Reuters

An anti-bullying charity warns that cyber-bullying can "spread rapidly like a cancer" and be so permanent it becomes "indelible like a tattoo."

Bullying comments that appear online on Web sites like Facebook and Twitter can "go global" and are very hard to have removed, according to Claude Knights, the director of the children's charity Kidscape.

Her warning comes as Jean Gross, England's communications champion, expressed fears that girls are exposed to bullying 24 hours.

"Now girls have got even more ways of excluding each other through communication... They used to do it just through verbal language, now they can do it through texting and de-friending and all of those things," Gross said ahead of her speech to the Girls' Schools Association in Bristol.

She added that an attitude of "girls will be girls" is preventing bullying from being taken seriously enough.

In 2010, an inquest heard how a 15-year-old schoolgirl, Megan Gillan, died from an overdose after being bullied on a social networking site.

"It is unfortunate in this day and age that the tentacles of harassment can reach outside the confines of school walls," said coroner Nicholas Rheinberg.

Another 15-year-old girl, Natasha MacBryde, killed herself after she was also bullied online.

A 2007 report found teenage girls to be most at risk from cyber-bullying.

Knights told IBTimes UK that a zero-tolerance approach needs to be taken to bullying, otherwise we risk "condoning" it.

"We don't want anyone to have to go through [bullying] as a part of growing up," she said.

Knights said she's seen cases of children as young as eight expressing suicidal thoughts because of bullying.

The rise of cyber-bullying in recent years has meant Kidscape's work needed to be "rethought".

"It comes up in every session we have," she said, adding it's a "significant issue" and applies to both genders, not just females.

Knights reiterated Gross's concerns about cyber-bullying's 24/7 nature.

She also highlighted "disinhibition", afforded to bullies by the lack of face-to-face contact with their victims and the opportunity to be anonymous online, as a serious problem.

"It removes the humanity," she said.

When face-to-face contact is made it "usually triggers empathy", which may stop the bullying or, at least, dampen the intensity.

However, face-to-face contact is often removed in a digital world.

"Keeping safe online needs to be addressed early on," Knights said.

"The way you equip people has to respond to these [problems]."

Parents and society have a responsibility to speak out and educate people about bullying and the "colossal effect" it has on victims, she said.

It is also important to work on people's self-esteem, she added, so they "don't collapse" when faced with bullying.