The two rabbits, one white and one dark grey, were found inside a white polystyrene insulated box in the car park of the health club in Rustington on Sunday (April 3), the charity said.
A member of the public found the bloodied and dead rabbits inside the box and contacted the RSPCA.
An RSPCA inspector is now investigating and the charity is appealing for information on what happened to the rabbits.
A spokesperson for the RSPCA, said: “This must have been very distressing for the member of the public who found these poor rabbits.
“Their legs were broken and they had a number of bloody injuries all over their bodies which may suggest they have been intentionally harmed.
“The juvenile rabbits were very cold so it’s not possible to tell how long they had been there – they could have been there for a while.
“We’re now appealing for anyone with information to please contact us. If you saw anything in Golfers Lane at around 9am on Sunday, or if you have any information about how these rabbits came to be injured, please contact us in strictest confidence, on 0300 123 8018.”
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