Fifty years ago, on 28 May 1959, the World Health Organisation's assembly voted into force an obscure but important agreement with the International Atomic Energy Agency – the United Nations "Atoms for Peace" organisation, founded just two years before in 1957. The effect of this agreement has been to give the IAEA an effective veto on any actions by the WHO that relate in any way to nuclear power – and so prevent the WHO from playing its proper role in investigating and warning of the dangers of nuclear radiation on human health.

The WHO's objective is to promote "the attainment by all peoples of the highest possible level of health", while the IAEA's mission is to "accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world". Although best known for its work to restrict nuclear proliferation, the IAEA's main role has been to promote the interests of the nuclear power industry worldwide, and it has used the agreement to suppress the growing body of scientific information on the real health risks of nuclear radiation.

Under the agreement, whenever either organisation wants to do anything in which the other may have an interest, it "shall consult the other with a view to adjusting the matter by mutual agreement". The two agencies must "keep each other fully informed concerning all projected activities and all programs of work which may be of interest to both parties". And in the realm of statistics – a key area in the epidemiology of nuclear risk – the two undertake "to consult with each other on the most efficient use of information, resources, and technical personnel in the field of statistics and in regard to all statistical projects dealing with matters of common interest".

The language appears to be evenhanded, but the effect has been one-sided. For example, investigations into the health impacts of the Chernobyl nuclear accident in Ukraine on 26 April 1986 have been effectively taken over by IAEA and dissenting information has been suppressed. The health effects of the accident were the subject of two major conferences, in Geneva in 1995, and in Kiev in 2001. But the full proceedings of those conferences remain unpublished – despite claims to the contrary by a senior WHO spokesman reported in Le Monde Diplomatique.

Meanwhile, the 2005 report of the IAEA-dominated Chernobyl Forum, which estimates a total death toll from the accident of only several thousand, is widely regarded as a whitewash as it ignores a host of peer-reviewed epidemiological studies indicating far higher mortality and widespread genomic damage. Many of these studies were presented at the Geneva and Kiev conferences but they, and the ensuing learned discussions, have yet to see the light of day thanks to the non-publication of the proceedings.

The British radiation biologist Keith Baverstock is another casualty of the agreement, and of the mindset it has created in the WHO. He served as a radiation scientist and regional adviser at the WHO's European Office from 1991 to 2003, when he was sacked after expressing concern to his senior managers that new epidemiological evidence from nuclear test veterans and from soldiers exposed to depleted uranium indicated that current risk models for nuclear radiation were understating the real hazards.

Now a professor at the University of Kuopio, Finland, Baverstock finally published his paper in the peer-reviewed journal Medicine, Conflict and Survival in April 2005. He concluded by calling for "reform from within the profession" and stressing "the political imperative for freely independent scientific institutions" – a clear reference to the non-independence of his former employer, the WHO, which had so long ignored his concerns.

Since the 21st anniversary of the Chernobyl disaster in April 2007, a daily "Hippocratic vigil" has taken place at the WHO's offices in Geneva, organised by Independent WHO to persuade the WHO to abandon its the WHO-IAEA Agreement. The protest has continued through the WHO's 62nd World Health Assembly, which ended yesterday, and will endure through the executive board meeting that begins today. The group has struggled to win support from WHO's member states. But the scientific case against the agreement is building up, most recently when the European Committee on Radiation Risk (ECRR) called for its abandonment at its conference earlier this month in Lesvos, Greece.

At the conference, research was presented indicating that as many as a million children across Europe and Asia may have died in the womb as a result of radiation from Chernobyl, as well as hundreds of thousands of others exposed to radiation fallout, backing up earlier findings published by the ECRR in Chernobyl 20 Years On: Health Effects of the Chernobyl Accident. Delegates heard that the standard risk models for radiation risk published by the International Committee on Radiological Protection (ICRP), and accepted by WHO, underestimate the health impacts of low levels of internal radiation by between 100 and 1,000 times – consistent with the ECRR's own 2003 model of radiological risk (The Health Effects of Ionising Radiation Exposure at Low Doses and Low Dose Rates for Radiation Protection Purposes: Regulators' Edition). According to Chris Busby, the ECRR's scientific secretary and visiting professor at the University of Ulster's school of biomedical sciences:

"The subordination of the WHO to IAEA is a key part of the systematic falsification of nuclear risk which has been under way ever since Hiroshima, the agreement creates an unacceptable conflict of interest in which the UN organisation concerned with promoting our health has been made subservient to those whose main interest is the expansion of nuclear power. Dissolving the WHO-IAEA agreement is a necessary first step to restoring the WHO's independence to research the true health impacts of ionising radiation and publish its findings."

Some birthdays deserve celebration – but not this one. After five decades, it is time the WHO regained the freedom to impart independent, objective advice on the health risks of radiation.