The number of animals used in experiments at the University of East Anglia (UEA) has almost doubled over the past two years.
Figures released by the university show the number of procedures carried out on mice has risen from 6,736 in 2016 to 12,190 in 2018.
A UEA spokesperson said the increase reflected the "expansion and diversity of research" into areas including cancers, infection and neurological diseases.
In 2016, the university carried out experiments on 7,136 animals - 6,736 mice and 400 frogs.
But in 2017, this increased to 11,082 procedures, carried out on 10,908 mice and 174 frogs.
And in 2018, the number rose again, to 12,190 mice and 228 frogs, a total of 12,418 animals.
However, the number of animals killed fell to zero in this time, with six mice killed in 2016, eight in 2017, and none in 2018.
The university stressed that all work with animals is regulated by the Home Office and UEA's own ethics committee, and researchers aim to minimise potential harm.
But UEA animal science and welfare student Johnathon Byrne, 28, urged the university to cut back on their animal research.
"I don't believe you can sacrifice even one animal just to benefit people's lifestyles," he said.
Mr Byrne, from Norwich, added: "We're in the 21st century - we've got the technology to not use animals at all in research to benefit humans via medicine."
Animal rights activist Gabriella Ditton, 25, added: "Animals are not here to serve us. They're not our property. It's about trying to cause the least amount of suffering."
Dr Mohammed Hajihosseini, an associate professor of biological sciences, said many procedures carried out are harmless, and added: "Most are routine, such as mating the mice to get the colony numbers up. You need to use the same as others have used to be able to compare like-for-like.
"Ten years ago we were only working on muscle and brain projects but with the increase in gut health there's been an expansion in using mice."
Dr Hajihosseini, who sits on the university's ethics committee, added: "Mice anatomy and physiology is remarkably similar to humans [and] their size and breeding cycle makes them an alternative to our closest relatives, primates.
"The increase in numbers reflects expansion and diversity of research carried out. Animal usage can fluctuate as researchers discover unexpected leads they need to follow promptly."
Ethics in animal research
The university says researchers take care to minimise animal suffering.
Licences for projects are issued by the Home Office and scientists are asked to outline in their applications how they will the reduce the number of animals used, and how they will share data with other researchers.
UEA's ethics committee is responsible to for ensuring researchers follow through on these commitments.
Dr Hajihosseini said: "Gone are the days when people would test shampoo on animals - 99pc of companies don't do that now.
"Things have really moved on from the days of those unnecessary procedures."
Researchers are asked to predict the severity level of their experiments in terms of hunger, thirst, discomfort, pain, injury, disease, distress, fear and freedom to express normal behaviours.
These fall under five categories: sub-threshold, or no suffering caused, mild, moderate, severe, and non-recovery, or death.
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