The animal welfare charity was contacted by a member of the public who made the shocking discovery on Saturday (25 August) in Spencer Street, Keighley, near Bradford.
RSPCA Inspector Becky Goulding, investigating, said: “The poor cat – a black and white adult female – was found laying on her back underneath the wooden pallet.
“It was an extremely upsetting scene and it must have been really distressing for the member of the public who found her.
“It’s extremely suspicious because the cat’s body was found underneath the pallet in the middle of a grass verge so it could not have fallen onto the cat accidentally.
“The cat was dead when she was found but I don’t believe she had been dead for long.”
Inspector Goulding spoke to neighbours but no one had heard or seen anything suspicious. She took the cat’s body to a vet who said they believe this was not an accident.
“Vets examined her body and believe this could not have possibly been an accident but rather that someone deliberately put the pallet on top of the cat and crushed her to death,” Inspector Goulding added.
“It’s absolutely hideous to think that someone could kill a cat in such a brutal and gruesome way, and it brings tears to my eyes to think of the suffering this poor puss must have endured.”
The RSPCA has launched an investigation and is calling on anyone with any information to contact the charity’s appeal line on 0300 123 8018.
“I’m sure someone living in the area must have seen or heard something so I’d urge anyone who might be able to help with this case to get in touch as soon as possible,” she added.
The cat was not microchipped and wasn’t wearing a collar or ID tag so the officer is also searching for her owner.