Relatively few countries around the world publish official statistics on animal research, and those that do substantially under-represent the true number of animals used, a new report claims.

The analysis of worldwide laboratory animal use in 2005 was published in the journal Alternatives to Laboratory Animals (ATLA) by researchers from the Dr Hawden Trust, a UK-based medical research charity that funds alternatives to animal experiments, and the British Union for the Abolition of Vivisection (BUAV).

They supplemented official figures from the 37 out of 179 countries (just 21%) that do publish data on animal experiments with extrapolations from a statistical model based on animal research publication rates in the same 37 countries during 2006. This produced a conservative estimate of 58.3 million animals used in 2005 by 179 countries with a human population greater than 200,000.

The researchers then adjusted these data for the estimated extra percentages of animals used in laboratories but excluded from national statistics – namely, animals killed only for tissue supply (21.1%), those used to maintain genetically modified strains (17.2%), and animals bred for laboratory use but regarded as surplus to requirements (59.3%).

This lifted the total estimate dramatically to 115.3 animals worldwide. Even that figure is likely to be an underestimate, the researchers suggest. The actual volume of animals used in laboratory experiments around the world could be 150 million or more.

Even in those countries that do issue official statistics, there are “unacceptable crucial omissions”, say the Dr Hawden Trust and the BUAV. For example, if the UK counted animals killed as surplus or for their tissues, this would take the Home Office’s published estimate of 2.8 million animals in 2005 up to 5.6 million animals used for research.

Moreover, just “basic accurate recording” in the US, which excludes an estimated 93% of animals used (all birds, rats, mice, fish, amphibians and reptiles) from its official data, would boost the published volume from a little over one million to 34 million animals, the organisations claim.

“It is impossible to have a clear and honest debate about the role of animal experiments in the 21st century when the official number of animals is outrageously underestimated,” they state. “It means a huge amount of animal suffering is simply being ignored, and efforts to replace animal research with more modern techniques are being hampered.”

In the new calculations published in ATLA, the US emerges as the heaviest user of laboratory animals with an estimated 17.3 million in 2005, followed by Japan with 11.2 million animals used.

The ATLA journal is published by the UK-based Fund for the Replacement of Animals in Medical Experiments (FRAME).