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.
"Medical research will wither in our universities and, as a result, more people will suffer and die," he wrote in a commentary Wednesday in The Times newspaper. Drayson called for the U.K. government to support the transport industry in opposing the animal activists.
More than 3 million animals are used in British lab experiments every year, of which about 15,000 are imported. Fewer than 1 per cent of the animals used in British labs come from abroad.
Dozens of airlines, including American Airlines, Cathay Pacific and Lufthansa, already refuse to fly bigger animals such as monkeys intended for medical research. In the U.K., such campaigns are supported by celebrities such as Ricky Gervais. Many of the larger lab animals, such as guinea pigs, dogs and ferrets, are bred within the U.K.
Scientists believe studying geneticall modified mice with genes for illnesses such as motor neuron disease, cancer and diabetes could help them uncover the causes behind them and lead to potential drug treatments.
Animal rights groups say it is morally indefensible to inflict pain and suffering on animals and that the scientific evidence for using animals in research does not justify their continued use.
P & O Ferries, one of Britain's largest ferry companies, decided in August to stop carrying research animals for the sake of their corporate reputation and to protect staff members from possible action by activists, said spokeswoman Michelle Ulyatt. She said transporting animals for scientific experiments was not a big part of the company's business.
"There was a sustained social media campaign against the company that blocked out email use for the entire board," Ulyatt said. "There were no direct threats, but we were put under enormous pressure and didn't want the situation to escalate."
She said she is unsure whether any government response would reverse the company's policy.
"Animal experiments are conducted in conditions of great secrecy, but the public is not fooled. They understand the massive suffering which is involved," said Michelle Thew, chief executive of BUAV, a British group that campaigns against animal testing.
U.K. science minister David Willetts said the British government is working with the transport industry and researchers to draft a code of conduct on how to import laboratory animals. If the refusal persists, such animals might only be carried by British military aircraft and ships, he said.