Almost a fifth of owners (18 per cent) are already falling into debt to pay for their pets' care, while 25 per cent said they will not take their pet to the vet due to the high cost, online pet marketplace Pets4Homes found.
Some 60 per cent of rescue centres saw a fall in pets being rehomed last year, with 42 per cent full up in 2022 compared to 22 per cent in 2019, according to the site's industry report.
A quarter of rescue centres (26 per cent) said financial reasons were most commonly given by owners handing over a pet to be rehomed.
Large dog breeds were most commonly given up for adoption, with German Shepherds and Staffordshire Bull Terriers topping the list.
Flat-faced dogs, such as pugs and French bulldogs, have declined in popularity after an increased focus on health issues among the breeds.
The fierce competition for a pet during 2020, when there were around 420 potential buyers for each pet advertised on Pets4Homes, has now stabilised to around 80 buyers.
Overall lower demand for pets is also reflected in prices, with the average cost of a dog or puppy falling from £2,065 during the pandemic to £995 – but still higher than the pre-pandemic £876.
Lee Gibson, UK managing director at Pets4Homes, said: "The cost-of-living crisis is already having a major impact on pets and their owners. The current challenges have resulted in a clear end to the boom in pet adoption and rehoming which defined the lockdown period, as cost is discouraging many from seeking a new pet.
"Yet the crisis is further proving that the international reputation of Britain as a nation of animal lovers is accurate as ever. Our findings reveal that the majority of UK pet owners will do everything in their power to keep and maintain their pets – already reducing expenditure and prepared to go to extremes should it be necessary.
"However, what is alarming is that pet ownership is already causing debt for some and that nearly one in ten of us is having to consider giving up our best friends.”
David Bowles, head of public affairs at the RSPCA, added: "Like the insights from the Pets4Homes report, the RSPCA has seen an increase in public concern on caring for their pets, with 19 per cent worried about affording to feed their pet.
"The 8 per cent of the public who say they are considering giving up their pet in the survey are now starting to be seen by the RSPCA frontline services, who have seen a 25 per cent rise in animals being abandoned in 2022 compared to the previous year.”