A full assessment of the public health impact has been thwarted by poorly co-ordinated research on residents in areas close to the plant, and should be carried out with funding from the European commission, said Keith Baverstock, a former health and radiation adviser to the WHO.
He said research had been frustrated by pro- and anti-nuclear lobby groups who had turned the debate over health risks into a battleground. Crucial lessons on how to respond to nuclear emergencies and quell public anxiety had been missed by governments and authorities such as the International Atomic Energy Agency (IAEA).
In an editorial in the British Medical Journal to mark the anniversary of the disaster, Baverstock calls for comprehensive research into cancers, birth defects and other health problems among 600,000 people in Belarus, Russia and Ukraine.
"Much could still be learnt and 'no evidence of health damage' after comprehensive investigation would be a valuable result," he writes. The project should be funded by the European commission and would cost €10m (£8.8m) for the first 10 years, Baverstock told the Guardian. A similar programme is under way to monitor the health of survivors of the nuclear bomb attacks on Japan in 1945.
The Chernobyl nuclear power plant exploded and caught fire on 26 April 1986, blasting vast quantities of radioactive material into the atmosphere where it drifted across European borders. Health restrictions are still in place at some UK farms after radioactive caesium from the plant blew over and contaminated pastureland.
The incident is thought to have caused 6,000 extra cases of thyroid cancer in people who were children at the time. Inaction by the Soviet authorities meant there was no ban on milk and other foodstuffs contaminated with radioactive iodine, which is now known to cause the cancer. In Japan, officials took swift action after the Fukushima power plant leaked radiation last month, distributing protective iodine pills to local residents.
The spread of radioactive material across Europe in 1986 led to widespread chaos as food bans were introduced in some countries and not others, and governments issued conflicting travel advice, a run of events now playing out in Japan, said Baverstock, who is now based at the University of Eastern Finland.
"Although information abounds, little of it is usable, especially in terms of determining the potential effect on public health, and its truthfulness is doubtful," the editorial states. In the first days of the Fukushima crisis, the engagement of both the WHO and IAEA "was notable by its absence", a situation Baverstock describes as "institutional failure".
After Chernobyl, the WHO set up a nuclear emergency project office to co-ordinate its response to future nuclear accidents, but the office was closed in 2000.
Baverstock argues that the health implications of Chernobyl have become a battleground for pro- and anti-nuclear lobbies that "seek to interpret the effects or absence of effects to their own advantage and are apparently unwilling to find the truth".
"Apart from exacerbating the psychosocial effects on those directly affected, this situation has prevented a comprehensive evaluation of the importance of the event to public health," he writes.
Geraldine Thomas, director of the Chernobyl tissue bank at Imperial College, London, said lifespan studies that monitor the health of people around Chernobyl would be valuable, if only to prove there were no other long-term consequences from the accident.
But she said putting too much emphasis on questions that may never be answered could raise unnecessary fears. "Telling a whole population that it may have health consequences at some point in its lifetime is not good for that population psychologically and we possibly do more harm than good in this respect," she said.