The WHO, responsible for the health aspect of the report, dramatically lowered the estimated Chernobyl death toll, suggesting confusion had been caused over the accident's impact.
Many emergency and recovery workers, the report suggested, had died since 1986 from natural causes which could not be attributed to radiation exposure.
But in its report, Greenpeace suggests there will be 270,000 cases of cancer alone attributable to Chernobyl fallout, and that 93,000 of these will probably be fatal.
But Blake Lee-Harwood, campaigns director at Greenpeace, told the BBC that cancer was likely to be the cause of less than half of the final fatalities.
"We're also looking at intestinal problems, heart and circulation problems, respiratory problems, endocrine problems, and particularly effects on the immune system," he told the BBC's World Today programme.
"The figures tend to converge around the 200,000 mark."
Child victims
Mr Harwood-Lee cited technical reasons for the discrepancy.
However, he also alleged that the nuclear industry had a "vested interest in playing down Chernobyl because it's an embarrassment to them".
Doctor Oxana Lozova, who works at a children's hospital in Rivne district, 300km (190 miles) west of Chernobyl, said many generations appeared to be affected.
"I think the fallout from Chernobyl has affected the immunity of those who were young children at the time of the disaster," she told the BBC's Moscow correspondent, Damian Grammaticas.
"We now have to deal with people who are a lot weaker than their fathers and grandfathers were.
"They're falling ill at an age when they really should still be quite fit."
'Apples and oranges'
The WHO said comparing the Chernobyl Forum and Greenpeace reports was like "comparing apples and oranges" when it spoke to the BBC News website.
"The Greenpeace report is looking at all of Europe, whereas our report looks at only the most affected areas of the three most affected countries," said WHO spokesman Gregory Hartl.
"The WHO felt it had recourse to the best national and international scientific evidence and studies when it came up with its estimates of [up to] 9,000 excess deaths for the most affected areas. We feel they're very sound."
Mr Hartl rejected accusations of bias toward the nuclear industry in the report.
"We acting as [neither] an apologist or an attacker of the nuclear industry," he said.
The original report found more than 600,000 people received high levels of exposure, including reactor staff, emergency and recovery personnel and residents of the nearby areas.
© BBC MMVI
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