The Queen and duchess have been accused of "ostentatious display of cruelty" after they were seen wearing real fur.
The two and other members of the royal family wore Russian-style hats made from various fox furs to a church service in Sandringham, though it cannot be confirmed if the Queen's hat was made of real fur.
"This strikes me as an ostentatious display of cruelty. To parade fur in 2010 says something unpleasant about the person wearing it," News.com.au quoted Animal Aid director Andrew Tyler as saying.
The Cossack-style hat worn by Camilla was made from "vintage fur" by designer milliner Philip Treacy, using a piece of fur, which had previously belonged to the duchess' mother.
It appears that many fashion designers are continuing to use fur in their collections, and campaigners have expressed fears that it could be coming back into style.
They have called on celebrities and members of the Royal Family to "set a good example" by choosing not to wear animal pelts.