Three-year-old Luna had gone out to play from her Olive Grove home in Goole when a neighbour spotted her and thought she was a stray, and called out an inspector from the animal charity.

Luna, a three-year-old tabby, was put to sleep by lethal injection the same morning, after it is claimed she became aggressive.

Her owners Harry and Jennifer Hamilton told the Courier that they were devastated by what had happened.

Harry (27) told the Courier: "She wasn't unwell and yet within an hour of collecting her they had put her down. They are saying she was ill but she wasn't, she was healthy.

"The RSPCA have gone against their policy and put her down with no real reason.

"We want to know why they have done it."

The couple, who have no other pets, have had Luna since she was four-and-a-half weeks old and have since brought her home and buried her in their garden.

"I'm absolutely gutted," added Harry. "She was a lovely cat and used to sleep between us. I've been really upset.

"My wife Jennifer is five-and-a-half months pregnant and she is absolutely devastated."

He added: "Luna had a collar on so obviously wasn't feral. I will be taking legal action against them."

A spokesman for the RSPCA said: "The RSPCA would like to apologise for this extremely upsetting incident. We would like to send our sincere apologies to the owners of the cat, and we will be speaking personally to them to convey our sympathies.

"The cat had been reported acting extremely aggressively, and the previous day a vet had been called in but was unable to catch the cat because of its wild behaviour.

"The cat seemed ill and feral and the reluctant decision was taken jointly with the vet to put it to sleep. "Nonetheless we fully understand how upset the family must be. The full circumstances of this incident are now being looked into so that we can understand how this happened."