The report by the International Agency for Research on Cancer predicts at least 40,000 people will get cancer . . . including 16,000 cases of one of the radiation-related thyroid cancer. Children living in regions closest to the plant at the time of the explosion will be the most heavily affected, because their thyroid glands were smaller than an adult's . . . suggesting that most Chernobyl cancer deaths are yet to occur.

The agency's figure is 10 times higher than the official figure for cancer cases which have occurred in the 20 years since the Ukrainian reactor exploded, on 26 April 1986, and double the last estimate for total deaths from the disaster. Countries closest to Chernobyl will be the most heavily affected . . . particularly Belarus, western Russia and the Ukraine. However, the report's estimates concentrate on countries within Europe, excluding large parts of central and northern Russia.

Dr Peter Boyle, the agency's director, said: ?The number of cancer cases in Europe possibly resulting from radiation exposure from the Chernobyl accident in the lifetime of the exposed populations is expected to be large in absolute terms."

Meanwhile, nuclear safety experts warned last week that tens of thousands of people living within 50km of Chernobyl face fresh risks of significant" radioactive leaks from the reactor. The vast concrete sarcophagus" now sheathing the plant is in danger of collapsing because it was so poorly built and maintained. The hazards of collapse of the dilapidated sarcophagus is significant, and growing year by year, " the two German nuclear physicists warned. At distances of up to 20km, the consequences are expected to be severe."

The concrete shell, erected 10 years ago, is now listing, sagging, and has substantial cracks, allowing rainwater inside. That water is creating pools of radioactive liquid inside the shell, and is believed to be leaking into the groundwater.

Thousands live illegally within the 60km exclusion zone around the plant, along with hundreds of people working to clear the site. If the sarcophagus collapsed, it would release a lethal" amount of radioactive dust in the immediate area, and cause radiation sickness for people hundreds of metres away.

The report, commissioned by Greenpeace, says the risks of a further accident at the plant are increasing because of delays in building a new steel dome to cover the concrete sarcophagus. The new ?shelter" is being substantially delayed, and is now expected to be erected in 2011 . . . some five years later than first expected, while costs have increased by 50% to $1.1bn.