Teenage girls are becoming more at risk of 'cyber-bullying', a new study has claimed.

Those who were bullied in this way - by text message or e-mail - are also more likely to have fewer friends and are more likely to feel lonely at school, the report by Nathalie Noret of York St John University and Professor Ian Rivers of Queen Margaret's University Edinburgh.

The report, which was presented at the British Psychological Society's Annual Conference at the University of York on Wednesday, was based on results from a survey of nearly 15,000 secondary school pupils over a period of five years.

The survey questioned pupils about their experiences at break times and how many friends they had, as well as asking them if they have ever received any nasty or threatening text messages or emails.

The results showed a dramatic increase in cyber-bullying over the last five years - from 14.5% in 2002 to 20.6% in 2006. However, while levels of cyber-bullying among boys showed both increases and decreases over the same period, levels of cyber-bullying among girls were consistent for every year.

Miss Noret said: "Bullying in schools is a serious problem and this research demonstrates that technology is supplying a new way of tormenting victims. As the levels of cyber-bullying are increasing, it is important to ensure that current anti-bullying strategies incorporate tactics to tackle this."