A United Nations report on the 1986 Chernobyl disaster underestimated effects from the accident, said an environmentalist's study released Tuesday in Kiev ahead of the 20th anniversary of the disaster.

Rebecca Harms, a German Green MP in the European Parliament, said she commissioned the study, "The Other Report on Chernobyl" or TORCH, after a UN report released last September said up to 4,000 people could die in Belarus, Russia and Ukraine as a result of the world's worst civilian nuclear accident.

"We commissioned TORCH to counterbalance claims made by the IAEA (International Atomic Energy Agency)... which played down the lethal consequences of the nuclear accident at Chernobyl and failed to make a meaningful analysis of its wider effects on Europe and the world," Harms said in a statement released with the report's findings at a news conference in Kiev.

"There must be no mistaking the catastrophic dangers that are still very much associated with nuclear power," she said.

The Greens' study said that fallout from the accident on April 26, 1986 affected many European countries.

"The largest concentrations of volatile nuclides and fuel particles occurred in Belarus, Russia and Ukraine," the report said. "But more than half of the total quantity of Chernobyl's volatile inventory was deposited outside these countries."

The study said that the number of cancer deaths resulting from the accident "most likely will never be fully known" but could be as high as 30,000 to 60,000.

Tuesday's study was the latest criticism leveled at the UN's report since it was released last September under the aegis of the IAEA and the World Health Organization.

Environmentalists and groups opposed to nuclear energy say the IAEA had downplayed the affects from the Chernobyl disaster to justify the continued use of nuclear energy.

On April 26, 1986, a reactor at the Chernobyl nuclear power plant north of Kiev in what was then the Soviet Union, exploded and sent a radioactive cloud across Europe.

Following the accident, a concrete sarcophagus was built over the stricken reactor and construction of a new 20,000-tonne steel case to cover the whole plant is planned between 2008 and 2009.

The power station was completely shut down on December 15, 2000.