About 115 million animals were used in scientific research globally in 2005, according to an estimate based on official national figures and extrapolations from the number of scientific papers that were published involving animals.
The vast majority of the animals used were rodents (83.5%) with primates, cats and dogs making up 0.15%, 0.06% and 0.24% of the total respectively.
The 115 million figure was difficult to compile because recording criteria differed greatly from country to country. Only 37 countries had even partial national figures, while the researchers estimated the numbers for a further 142 countries based on the number of publications involving animals that came out in 2006.
The global estimate was put together jointly by the British Union for the Abolition of Vivisection and the Dr Hadwen Trust for Humane Research and is published in the journal Alternatives to Laboratory Animals. "It is shocking that so few countries consider it important even to count the number of animals suffering in their laboratories," said the groups.
"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 involved is outrageously underestimated."
The final figure is also inflated by animals that would not be included in the UK figures - for example surplus animals produced during breeding which are not used in research and animals that are humanely killed so that their organs or blood can be used for research purposes.
In Britain, researchers must record the number of animals they use, the number of procedures they carry out and the number of breeding animals used in GM breeding. But in the US, the largest user of research animals - more than 17 million according to the researchers' estimate - official figures do not include mice, rats, birds, fish, reptiles and amphibians.
Most countries record no figures at all and Liechtenstein and San Marino are the only countries to have banned research involving animals altogether.
© 2008 The Guardian