The number of animal experiments carried out in the UK rose by 8% in 2012, according to Home Office figures.
The rise is due to an expansion in the use of genetically modified animals.
According to the way the Home Office classifies statistics, procedures on GM animals were higher than the number on non-GM animals for the first time.
Campaigners criticised what they said was the government’s failure to deliver on a post-election pledge to cut the number of procedures.
About 4.11 million scientific experiments on animals took place in 2012, an increase of 317,200 on the previous year.
The number of GM animals increased by 22%; this year saw 1.91 million genetically modified (GM) animals used compared to 1.68 million non-GM animals.