Medical research in the U.K. is being jeopardized by activists who have persuaded transport companies to stop importing mice, rats and rabbits for scientific experiments, a former British science minister says. The boycott affects only a tiny proportion of laboratory animals, but scientists say these particular animals are the most important ones for their research.

Following campaigns by animal rights groups, several ferry companies and airlines, including British Airways, now refuse to carry mice, rats and rabbits destined for laboratories. The Channel Tunnel, which links the U.K. to France, has long refused to allow any animals for medical research to be transported. Only foreign airlines still carry such animals into Britain. Paul Drayson, a former science minister, said that is “choking off vital research” into deadly diseases such as Alzheimer’s and cancer.