Princess Michael of Kent has reportedly stated animals do not have rights "because they don't pay taxes".
Her alleged comments sparked a backlash from animal rights campaigners who have branded them "ignorant".
The princess, who is married to the Queen's cousin, is said to have made the remarks at Henley Literary Festival during a discussion about her new novel, Agnes Sorel: Mistress Of Beauty.
"I'm a great animal lover and I'm involved in a lot of conservation, but animals don't have rights. They don't have bank accounts. They don't vote," she reportedly said.
"We have obligation. We have obligation to animals, but to say they have rights?
"They don't have rights. You only have rights if you pay your taxes. You earn your rights."
The princess has previously clashed with animal rights campaigners over her love of fur coats.
Elisa Allen, associate director of People for the Ethical Treatment of Animals (Peta), told The Times: "Peta urges Princess Michael to study the subject, rather than making an off-the-cuff statement that reflects ignorance of the issue of what fundamental rights animals have, which do not include the right to drive a car or build up an overdraft.
"She should also exercise caution in opining at all on such issues, because her daft assessment would mean that children and certain classes of human beings are also not entitled to rights."