Cat owners have been advised they could risk breaking the law if they force their pets into veganism.

One in six pet food suppliers has branched out into supplying vegan or vegetarian food for animals as owners embraced the new trend over ethical concerns with meat diets.

But yesterday the RSPCA said cats could become seriously ill if given exclusively plant-based diets and owners could run the risk of getting a criminal record.

A spokesman said while dogs were omnivores and could theoretically survive on a vegetarian diet, cats were carnivores and needed meat.

They pointed out: "Under the Animal Welfare Act, the law requires an owner to take reasonable steps to ensure that all the pet's needs are met.

"This includes a healthy diet, as well as providing suitable living conditions, ability to behave normally, appropriate company and protection from pain, suffering, injury and disease."

In the worst cases where cats are so malnourished, guidelines say owners could face a hefty fine or even a jail sentence if convicted under the Animal Welfare Act.

The warning comes after the National Pet Show in Birmingham earlier this month showcased the latest in vegan pet food and non-meat alternatives, as owners look to spread their ethical diets onto their pets too.