British scientists believe that following Brexit the scientific clock could be turned back in the country on animal testing techniques.
The National Anti-Vivisection Society (NAVS) is concerned that hard-fought EU regulations on animal experiments could be rolled back in the UK.
Government figures released today shows that four million animals were used in the country for research last year.
"With the introduction of advanced scientific methods, we and the public expect to see year-on-year reductions in animal use, so this increase is not what the public wants," Jan Creamer, President of the National Anti-Vivisection Society said.
"The prospect that Brexit could turn the scientific clock back, returning to outdated methods, is a real concern," he added.
Researchers in the UK have previously called for less regulation and may well now press for "cutting through the EU red tape" to make it easier to test on animals, with less scrutiny and oversight.
While the UK is unlikely to allow cosmetics testing on animals, the EU Cosmetics Directive also bans the import of products that have been tested on animals.
This key Directive prevents countries such the US, China and others from selling their cosmetic products in Europe if they have been animal tested.
Brexit may also jeopardise proposals to phase out laboratory primate use. The EU proposals to end the use of monkeys born from parents caught in the wild would be weakened if the UK does not demand the same standards.
The EU plan would stop monkey dealers in Mauritius, Vietnam and elsewhere, from restocking their factory farms with animals captured in the wild. The UK itself does not currently use monkeys born to wild caught parents.
