Seven in ten said their premiums had increased since they last renewed their policy.
Dog owners pay an average of £420 a year for pet cover, while it costs £264 for a cat.
Those with dogs aged ten to 12 pay 80 per cent more on average, compared with owners who have pets under four.
It is typically 76 per cent more expensive to insure older cats than those under three.
But dozens had to spend more than £1,000 a year on cover, according to the Which? survey of 1,100 members.
At renewal, premiums typically rise by £84 for dogs and £40 for cats.
Half of adults in Britain own a pet, according to the charity PDSA.