Incidences of cancer among children living along the north Wales coast is not linked to discharges of nuclear waste, claim health officials.
The report says firm conclusions could not be drawn
Disease rates around the Menai Straits were studied by the Welsh Cancer Intelligence and Surveillance Unit.
It said levels of leukaemia had increased recently, but involved small numbers of cases.
It was responding to concerns by Green Audit, an environmental consultancy in Aberystwyth.
Green Audit claimed the study proved nothing and that child cancer rates were still high in north Wales.
However, WCISU's work has been supported by a report from the National Public Health Service for Wales (NPHS) on childhood cancer incidence in Gwynedd and Anglesey.
Meanwhile, the Committee on Medical Aspects of Radiation in the Environment (COMARE) praised the analysis of cancer rates by NPHS and WCISU and criticised Green Audit.
Comare said Green Audit's analysis had "several significant weaknesses and cannot be regarded as reliable."
Dr Chris Busby of Green Audit disagreed and claimed it was "an attempt to rubbish me."
Green Audit was funded by the Irish government between 1997 and 2000 to analyse Welsh cancer register data. Ireland did not have a cancer register.
In a report in 1998, Green Audit claimed cancer rates among children in north Wales were linked to alleged discharges from Sellafield nuclear power station, in Cumbria.
Four Irish people then took British Nuclear Fuels to court on allegations of polluting their bodies, which the power company denied. The case subsequently stalled.
Andrew Jones, leader of the environmental team for NPHS Wales, said people living in north Wales could be reassured by its statement.
Dr Chris Busby disagrees with the latest report
"There is no evidence of an increase in retinoblastoma or in tumours of the brain and spine in the Menai Straits area.
"Although WCISU did find levels of childhood leukaemia that were raised in the more recent period, their studies involve small numbers of cases which makes it impossible for firm conclusions to be drawn."
John Steward, director of WCISU, said: "In studies involving such small numbers of actual cases it is not possible to conclude whether findings are unusual or simply due to random chance.
"WCISU is committed to continuing with our ongoing surveillance and geographical analysis of childhood cancers across the north Wales coastline and this has been supported by COMARE."