The research, released on Sunday at the annual meeting of the American Psychological Association, comes amid reports that the European Union is considering draft guidelines which will allow addicts to receive clinical treatment in the same way as alcoholics.

"Marriages are being disrupted, kids are getting into trouble, people are committing illegal acts, people are spending too much money," said psychologist David Greenfield, who conducted the study.

"As someone who treats patients, I see it."

The researchers warned that compulsive Internet surfing was now a more serious problem than lottery addiction.

The EU is reportedly considering a policy which will allow addicts to seek help from their countries' national health services.

Escape from problems

The 17,000 participants in the survey answered a questionnaire based on questions which have been used in studies of gambling addiction.

They were asked whether they had taken to surfing to escape from their problems, whether they had tried unsuccessfully to spend less time at the computer, and whether they remained preoccupied with the Internet when they were no longer surfing.

Participants who responded positively to five or more of the 10 questions were regarded as being addicts.

Nearly 1,000 people - 5.7% of the participants - gave five or more positive answers.

The question which received the greatest number of positive responses - 30% - was about whether users regarded surfing as an escape from problems.

Representative sample?

Earlier research on Net addiction - based on studies of college students - suggested that as many as 10% of surfers might be addicts.

But the researchers in the new study warned that their findings were based on a questionnaire which was accessed only from the ABC News website - implying that the respondents might not be a representative sample of Internet users.

The survey followed high-profile TV coverage of Internet addiction, which could have prompted people who considered themselves addicts to take a particular interest in the questionnaire.

But researcher Kimberly Young said the new study was broad enough to add "a layer of legitimacy to the concern that Internet addiction is real".

'More satisfying than my husband'

One self-confessed addict who wrote to ABC earlier this year described Internet auctions as "worse than cigarettes and just as expensive as gambling".

Another user wrote about discovering chat rooms.

"I rapidly recognised the computer was more satisfying than my relationship with my husband or daughter," she wrote.