Experts claimed that the Russian-style hats they donned to attend a church service in Sandringham, England with other members of the royal family were made of fur from different types of fox, the Daily Mail reported.
Andrew Tyler, director of Animal Aid, said: "This strikes me as an ostentatious display of cruelty. To parade fur in 2010 says something unpleasant about the person wearing it."
The hat worn by Camilla was made of "vintage fur", by designer milliner Philip Treacy, using a piece of fur which had previously belonged to the duchess's mother.
A spokesman for the Queen said she could not confirm if her cream-coloured hat and matching coat trim were made of real fur, the report said.
Many fashion designers continue to use fur in their collections, and campaigners have expressed fears that it has come 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.
The Queen has worn fur in the past and her official robes for State occasions are trimmed with ermine, the winter coat of the stoat.
Camilla faced anger from animal rights organisations last year, when she wore fur twice during an official visit to Canada.
First she wore a grey rabbit stole when she visited Newfoundland, together with a hat trimmed with fake fur. She then donned a calf-length cape lined with grey fox fur.
Both pieces were said to have been "refashioned" from vintage fur.
The ethical question of "recycling" vintage fur has split opinion, but Tyler said: "It doesn't matter when the animal was killed, it's a body part and a product of cruelty."
In 2000 Prince Edward's wife Sophie apologised after she was seen wearing a fox fur hat. The Countess of Wessex said her decision to wear the hat on a skiing holiday in St Moritz, Switzerland, was "an error of judgment".
Legislation to ban fur farming in Britain was passed that same year following a lengthy campaign highlighting the physical and psychological distress suffered by animals in some fur farms.
However, it remains legal to import fur and in China, now the world's leading fur exporter, millions of animals who are killed for their fur are often skinned alive, according to the campaign group People for the Ethical Treatment of Animals (PETA).
"Britain is a nation of animal lovers and more than 90 percent of Britons refuse to wear fur," a PETA spokesman said.
"We hope that the queen will choose to wear something more humane in future, that better reflects the values of the British people," the spokesman said.