One in three pets are overweight and most owners do not think they can do anything about it, according to a survey.
Research shows only a third of cat and dog owners who thought their pet was overweight believed they could do "a lot" about its weight.
A third of cat, dog or rabbit owners admitted feeding their pets too many treats, with the same amount saying a lack of exercise contributed to their pet's weight problem.
One in 10 admitted over-feeding their pets at mealtimes and when asked which picture most closely resembled their pet, only 33% of dog owners and 23% of cat owners chose the "normal weight" picture.
Chief executive of the Pet Food Manufacturers' Association Michael Bellingham said: "Pet obesity has a serious, and sometimes fatal impact on the health and welfare of our pets.
"The figures are alarming and the problem won't go away without a fundamental shift in owners' attitude to feeding their pets. It is also worrying that most owners are not aware of the problem, because they are unable to recognise a fat pet in the first place.
"Perceptions of what is the correct size are seriously out of kilter with reality."
Only a quarter of the people surveyed said they had ever sought advice on whether their pets were overweight.
The research was carried out on behalf of the Pet Food Manufacturers' Association in March 2009 and surveyed 2,126 UK households.
