The survey also showed up to two-thirds of users did not receive any treatment for their addiction in the 12-month period of study.

The study, published on Thursday, was commissioned by the Drug and Alcohol Unit of the Department of Health.

This will enable us to more effectively plan and target services

Jo Daykin Drug and alcohol co-ordinator

According to the survey, users in Ballymena, County Antrim, were more likely to be male, younger, and injecting more than in other areas.

The report said users in Belfast were more likely to smoke than inject.

It is believed to be the first study of its kind into the scale of usage in Northern Ireland.

'Manageable level'

Northern Ireland Drug and Alcohol Strategy Co-ordinator Jo Daykin said: "It provides a reliable baseline of the number of problem heroin users. This will enable us to more effectively plan and target services."

She added: "It is fairly clear that heroin use in Northern Ireland is rising, but it has not reached epidemic proportions.

There have been pockets of heroin use in Belfast in the 80s, 70s and 60s, although it was probably masked by the wider political conflict

Dr Karen McElrath Queen's University

"It is still at a manageable level and the programmes we have in place are working.

"The treatment is having an impact and we now have to take this research and bring it forward and ensure that any gaps in provision are addressed."

The report estimated the number of problem heroin users in a 12-month period from November 2000 to October 2001.

Problem users are described as individuals who had experienced significant "social, psychological, physical or legal problems associated with dependence, intoxication or regular consumption" of heroin.

The report also found during the 12-month period of the study, between 36 and 52% of problem heroin users received treatment.

It was carried out by Dr Karen McElrath of Queen's University in Belfast.

Dr McElrath said heroin had been in use in Belfast since the 1960s.

"There have been pockets of heroin use in Belfast in the 80s, 70s and 60s, although it was probably masked by the wider political conflict," she said.