RSPCA animal shelters across the country are being inundated with cats and kittens in desperate need of new homes, the charity announced this week.
The animal charity said many of its rehoming centres were completely full of cats who had been dumped by their owners or rescued by RSPCA inspectors.
Although it is the peak birthing season for cats, the RSPCA said lots of centres were looking after more cats and kittens than ever before.
Since the beginning of 2009, an average of 21 cats have been taken in every day at the charity's 16 regional centres, with other independent branches and shelters suffering a similar plight.
Between January 2010 and July 2010 a total of 4,135 cats have been taken in to RSPCA care.
The charity is appealing for new owners to provide permanent, loving homes to the animals, as many are currently being kept in private boarding homes or foster homes as the RSPCA centres are simply too full.
The Enfield and District RSPCA branch is looking after about 90 cats and kittens, which is more than it has had in at any one time over the past 35 years.
Branch secretary Margaret Marden said: "It's really dreadful at the moment, this is the worst I have ever seen the situation. It's so hard for us to see all these beautiful cats and kittens without the homes they deserve."
The Little Valley Animal Shelter in Exeter is currently looking after 42 cats despite only having space for 32 and it is still getting regular requests from the public and RSPCA inspectors to accommodate even more.
Christine Kerridge, from the RSPCA central and North-east London branch, which is currently looking after more than 100 cats and kittens, said: "So many people are letting their cats get pregnant without giving any thought to how they will find good homes for the kittens.
"We are left to pick up the pieces. We really need new owners to come forward to give a second chance to the many delightful cats who are without a permanent home through no fault of their own."
The RSPCA is urging people considering getting a cat or a kitten to avoid answering ads in newspapers or visiting pet shops, but to take home a rescue animal.
The charity charges an adoption fee of around £50 to £60 for each cat, which includes a neutering operation, microchipping, a full veterinary check, worming and flea treatment and any vaccinations the cat may require.
The rehoming process aims to make sure the cat and owner are suitably matched, which includes a home check and follow-up visits in some cases.
The RSPCA is an animal welfare charity best known for its rescue and rehoming work with cats and dogs, but which responds to all animals in need, including wildlife, farm animals and laboratory animals. For more information go to http://www.rspca.org.