IT could take just one un-neutered female cat to be responsible for a staggering 50 million offspring, according to figures released by the RSPCA.

And, insists the charity, this figure is "conservative".

But with a free mobile neutering service to be launched next year they hope owners will be encouraged to take responsibility for their cats.

As to the current situation, Zoe Orchard of Bolton's Destitute Animal Shelter explained: "We are absolutely full of lost, stray or abandoned cats, and the problem is escalating all the time.

"The main reason is because so many people do not have their cats neutered. It really should not be an excuse. It is not an expensive operation and, if they are short of money, the RSPCA can help."

And the RSPCA, along with the Animal Shelter, believes that the problem could turn into a crisis after Christmas as the massive number of kittens born this year will be old enough to have their own young.

The charity also believes the fact that many owners do not realise the importance of having their cats neutered is also part of the problem.

"There is really no excuse for Bolton's cat owners not to have their pets neutered," said Kathy Kay of the Bolton branch of the RSPCA.

"We have a fantastic scheme in the town where a number of vets will, in conjunction with us, perform the operation at a greatly reduced rate.

"For example, it usually costs between £35-£40 to have a female cat spayed and between £27-£30 for a male.

"For those people on low income or who are unemployed, the reduced costs are £10-£12 for a female and £6 for a male cat.

"And I believe if someone can't afford that, then they shouldn't have a cat."

She also points out that the mobile RSPCA neutering service for the Bolton area is "in the very early discussion stage".

She explained: "There is a pilot scheme operating in another part of the country but we would need sponsorship for it to happen here. However, we are optimistic and hope it happens sooner rather than later."

Chris Laurence is head of the RSPCA's veterinary department and said that kittens born this year are coming into season.

He added: "Unless owners get them neutered now we are going to see severe problems in the New Year. Many animal centres are overcrowded and already have long waiting lists."

Zoe, of the Destitute Animal Shelter, agrees. She said: "We have an extremely long list of cats waiting to come in but we just don't have the room. It's a desperate situation."

Because the RSPCA can only deal with injured strays, Kathy explained that they do not have the funds or facilities to deal with every stray.

It is the other animal centres, such as Pets in Need and the Cats Protection -- formerly Cats Protection League -- who have to deal with the others.

In recent years, cats have overtaken dogs as the most popular household pet. Yet, last year, the RSPCA found new homes for about 46,000 cats -- 6,500 in the North-west.

A spokesman for the charity said: "Many cat owners are not aware of the consequence of uncontrolled breeding.

"Cats have been bred to be domestic over hundreds and hundreds of years, so they can't just revert to being wildlife and don't survive well in the wild.

"They suffer from the weather and difficulties in finding food."

The RSPCA calculates that by neutering nine out of 10 cats, the population should stabilise. But it is vital that the public acts now to avoid the situation getting out of control.

Chris added: "The mobile unit will tackle some of the worst affected areas in the country and will be launched at the beginning of next year."

However, Kathy stressed: "While this unit is a fantastic thing, owners should not wait for it to arrive in Bolton to have their cats neutered.

"They should visit the vets offering the reduced payment service.

"Unfortunately, all too often, we see at first hand what can happen when the public ignores this message.

"It is bad enough in Bolton. It is up to pet owners to make sure it does not get any worse." Local tales of horror in the Bolton and Manchester area A young cat and its three kittens were found shivering inside a cardboard box after being dumped near an office. A caretaker discovered them and described the kittens as being so small they would fit into a cup. Attempts are now being made to find them all permanent homes.

Two cats were abandoned and were so underweight their bones were clearly visible. They were also suffering from a skin complaint caused by a flea allergy that had been left untreated for many months. RSPCA staff gradually gained the frightened pair's trust and they are now recovering and being sought new homes.

A 10-year-old cat was in such a terrible condition after being dumped in a cardboard box in heavy rain that a vet had no option than to put it to sleep. The weather was so atrocious that the box was an unrecognisable pulp. An RSPCA spokesman said: "The cat had just sat there with what remained of the box surrounding it. It had been raining heavily for at least three hours. The cat had hypothermia and never flinched when I picked her up and collapsed once we got her inside. The vet took one look at the cat and decided to euthanase her on humane grounds."