Veterinary surgeons are warning that cat and dog owners are spending tens of millions of pounds on unnecessary and sometimes dangerous vaccines.
Vets say dog owners are spending millions on unnecessary vaccines
More than 30 vets have signed an open letter warning many vaccines for pets given in yearly doses last much longer.
They have accused the pharmaceutical industry of "fraud by misrepresentation, fraud by silence and theft by deception".
But drugs companies say they are bound by rules from licensing authorities.
Because of a lack of research it can only give a minimum period of immunity - usually 12 months.
The vets are warning the pharmaceutical industry and their own profession about the issue.
In their letter they say that vaccinations for many conditions including distemper, cat flu and parva virus, last a lot longer than a year and sometimes for life.
The letter said: "The present practice of marketing vaccinations for companion animals may constitute fraud by misrepresentation, fraud by silence and theft by deception."
BBC correspondent Angus Stickler said that vets send out computer-generated letters telling people to take their pets in for vaccinations "every year, year in, year out".
He said: "With £20 to £40 to pay and about 13m dogs and cats in the country it's an industry worth tens of millions of pounds."
The letter also talks about an increase in the risk of "adverse post-vaccination events" including a list of problems such as auto-immune disorders, transient infections and a risk of cancer in cats.
Vaccination manufacturers say that, although they can test animals for one or two years so they can give a minimum cover or immunity, it is difficult to perform lifelong tests.
They say that to prove immunity lasts for three or four years, or for life, would mean keeping and testing a large number of cats and dogs for years on end.
David Sutton, a spokesman for Intervet, one of the world's largest veterinary drug manufacturers, told BBC Radio 4's Today programme: "We base our recommendations on the science and the science we have tells us that we don't know how long immunity lasts in any individual animal.
"What we do know is there are some animals that need more frequent vaccination than others and our vaccine recommendations have to be based on taking account of those animals."
The vets' warning comes as more than 6,000 vets from all over Europe gather in Birmingham for the world's largest congress devoted to domestic pet welfare.
One of the techniques up for discussion at the four-day event is pheromonotherapy, used to help cats and dogs overcome fears and phobias.
The treatment is based on a study of chemicals, called pheromones, secreted by canines and felines through glands on their body.
These convey messages to members of the same species about ownership of territory, gender and mating availability.