A study from Stanford University School of Medicine in California found that "problematic internet use" was present in a sizeable portion of the population.

The study found that many of the respondents admitted that they wanted to spend less time surfing the internet but found it difficult to cut back, with almost six per cent saying that their excessive use had badly affected their relationships.

Elias Aboujaoude, the study's lead author, said in a statement: "We often focus on how wonderful the internet is - how simple and efficient it can make things. But we need to consider the fact that it creates real problems for a subset of people."

The findings of the telephone survey of 2,581 people, selected randomly in the US during the spring and summer of 200, was published in the October issue of the journal CNS Spectrums: The International Journal of Neuropsychiatric Medicine.

Researchers asked a number of questions, including whether respondents felt preoccupied when offline and whether any of their relations suffered as a result of their internet use.

The study found that 68.9 per cent of respondents were regular internet users and that 13.7 per cent found it hard to stay offline for several days at a time.

Some 12.4 per cent said they often stayed online longer than they had intended, and more than 12 per cent said they needed to cut back on their internet use. A smaller number, 8.7 per cent admitted to trying to conceal "non-essential" internet use from family, friends and employers.

From the respondents, 8.2 per cent said they used the internet to escape from their problems, and 5.9 per cent felt their relationships suffered because of excessive use.

The internet community has been quick to respond to claims that users have become addicted with a variety of self-help groups, surveys and organisations offering advice to addicts springing up on the web.

The Stanford study follows several other reports over the past decade that have concluded that internet use can be addictive, including online gambling and the compulsively visiting of pornography sites.

Mr Aboujaoude said: "Not surprisingly, online pornography and, to some degree, online gambling have received the most attention - but users are as likely to use other sites, including chatrooms, shopping venues and special interest websites."

Internet chatrooms have been a source of concern for parents in the UK after reports that paedophiles were posing as youngster in the hope of befriending children.

Research has revealed that millions of young teenagers use internet chatrooms, and nearly 10 per cent have put themselves at risk by meeting someone they contacted this way.

A study of 1,500 youngsters aged 9 to 19 by the London School of Economics found that more than half had viewed explicit material on the internet and that a quarter had been sent pornographic spam.

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