If people find a stray cat they need to get in touch with the SPCA straight away to avoid an influx of unwanted kittens, she said.
"People just don't think. We are just becoming a dumping ground for these unwanted pets. As a result we have got no room now. We have four empty beds for an emergency only. It's not good enough."
Staff operate a trap, de-sex and return programme for wild cats and would rather de-sex a stray than leave it until it had kittens and they all arrived on the doorstep, Mrs Rolfe said.
"It just becomes a bigger problem for us to deal with ... It's very stressful on the animals with so many in one room. They get sick because we have so many of them."
They remind people not to give a cute kitten, cat or dog to a child as a gift this Christmas unless they have first checked with the child's parents.
The SPCA has gift vouchers they are making up for people to buy as gifts so recipients can pick their own pets.
"That way they will get a pet they want."
As for donations of food, animals taken in are all fed the same food, so SPCA would prefer that people gave a cash donation so the SPCA could buy the food needed from VetPlus at a "heavily discounted" rate, Mrs Rolfe said.