Thousands of extra kittens could be born this summer due to lockdown restrictions, with animal welfare charities already feeling the strain of the “kitten crisis”.

Cat owners are being urged to keep female cats indoors as the number of kittens being born is expected to rise, with the seasonal boom exacerbated by the UK’s lockdown restrictions.

Around 84,000 extra kittens could be born because fewer vets are carrying out neutering procedures.

One man from Harrow found himself with a house full of 17 cats during the lockdown after his unneutered female cat became pregnant. The situation quickly spiralled, with multiple litters being born at the same time.

The charity said: “The issue arose when an unneutered female gave birth to a litter of four.

“A young male in that litter mated with his own mother and sisters, who delivered their own litters, and the population escalated to 17 cats.”

The kittens were taken into the care of Cats Protection and they will eventually be rehomed.

The RSPCA also rescued 22 cats from a single household in Weston-super-Mare this week. The cats, including 14 different kittens from three different litters, also included several pregnant adult cats.

The charity said the number of kittens born in the house had grown rapidly because, due to lockdown, vets have only been carrying out emergency procedures, which does not include neutering.

Since lockdown began, the RSPCA has taken more than 600 cats into its care – more than any other pet – and fears the situation could get worse.

From kittens dumped in carrier bags to strays found outside supermarkets, many cats and their kittens have been abandoned during the lockdown, with both charities being forced to step in.

Among those was a pregnant cat, abandoned in Sheffield after its owners moved away and who is now being fostered by an RSPCA inspector. The kittens are now four weeks old and have been joined by a single three-week-old kitten, Luca, who was found under some decking on his own and had to be hand-reared.

A six-month-old stray cat was found by a member of the public struggling to give birth in Hyde in Greater Manchester at the start of May. The cat was taken to the vets for an emergency c-section but sadly three of the kittens died.

The RSPCA has had 6,630 incidents reported to them involving cats since March 23. Although the volume of calls being received during lockdown is less than the same time last year, the charity is now only responding to emergencies.

Dr Samantha Gaines, head of the RSPCA’s companion animal department, said: “The kitten season this year will continue despite Covid-19 and so the charity is bracing itself for even more cats.”

A survey of 1,000 cat owners by Cats Protection found that 86% did not know that a female cat can have up to 18 kittens a year, while 77% were unaware a female cat can become pregnant as early as four months of age.

The charity is now urging owners to separate male and female cats and keep unneutered cats indoors until vet surgeries become fully operational again.

Sarah Reid, the charity’s acting head of neutering, said: “Our fear is that many kittens born this summer will be left on the streets. This is because Cats Protection is full up with cats and, owing to Covid-19, is unable to admit many more except in emergency cases.”

Cats Protection has been trialling hands-free rehoming while its centres remain closed.

So far 1,000 cats have been rehomed this way, which involved a virtual meet-up before the cat is delivered to its new home. The new system is being phased out across the charity’s centres.