The charity was alerted by the cats’ owners, distraught at the death of their pets, who suspected the worst.
Inspector Jennifer Surgeon said, “After being made aware of a suspected poisoning, both of the victims were sent away for a post mortem, the results of which confirmed our fears.
“Ethylene glycol is highly poisonous to cats and causes a very slow, painful death.
“In this case both cats lived in close proximity to each other (in Livingston) so we are dealing with what appears to be a very cruel and deliberate act.
“It is essential that everyone stores anti-freeze out of reach of cats and other animals. “There are strict guidelines for use and anyone who uses this substance to cause deliberate harm is committing an offence.
“Owners whose cats appear unwell should seek immediate veterinary treatment as early detection offers the best chance of survival.
“Without any other evidence we cannot say whether these poisonings were deliberate or accidental so we are appealing to local residents to contact us if they have any information in relation to these concerning incidents.”
Anyone with information is urged to contact the animal helpline in strict confidence on 03000 999 999.