The news comes on the eve of National Spay Day, an initiative to educate owners about the importance of neutering their pets.
According to a 2018 report by the PDSA, up to a million cats remain unspayed. Nearly a quarter of owners said they hadn't even considered neutering their pets, while others believed their cats were too young to fall pregnant.
Most cat pregnancies are "unplanned"
The report helps explain why an estimated 70% of all cat pregnancies are unplanned.
The UK cat population is believed to be around 11million, and the RSPCA has seen a sharp rise in the numbers of strays and unwanted cats.
Last year, the RSPCA animal welfare line received over 150,000 calls in regards to cats in distress. Officers worked around the clock to save 22,000 cats, making felines the most recused animal in the UK.
Kittens producing kittens
The Cat Population Control Group (CPCG) believes spaying kittens at four months is the best way of preventing large amounts of unwanted pregnancies. Traditionally, cats are spayed at six months. This has led many owners to the erroneous assumption that younger kittens can't fall pregnant. In fact, a significant number enter their first heat season at four months.
Carrie Stones is a cat population control manager at the RSPCA. She told the Express, "The UK is facing a cat overpopulation crisis as there are simply not enough homes for the large number of cats we and other charities see. We believe the answer is to neuter cats from four months old to ensure that no more unwanted litters are born."
World Spay Day is on the 26th of February. It's supported by nine of the UK's animal welfare charities and provides information on pet neutering, including how to get help with the cost of spaying your cat.