It costs the branch more than £26,000 every year to look after the cats in its pens, and the winter months are always particularly busy with more abandoned pets than it can cope with.
Supporters can donate £6.50 to sponsor a pen of their choice for one day, or more if they wish.
“All your money will help all the homeless cats to spend a safer Christmas in a place where they are looked after,” said a spokesman for the RSPCA branch.
“The help of our donors is so important and we can’t manage without it, so please do something kind this Christmas and make a contribution toward a cat that through no fault of its own is unwanted.
“It can be in memory of one of your cats, to sponsor the pen where your adopted cat came from, or as a Christmas present to an animal lover,” the spokesman added.
For more details or to get involved and sponsor a pen, visit www.mydonate.bt.com/ events/sponsorapen