The organisation blasted Rihanna for wearing snakeskin boots during a trip to London last week, while Gaga also came in for criticism in a fresh attack.
A statement issued by PETA read: "Rihanna may not have a clue that snakes killed for boots are often nailed to a tree and skinned alive. Of course, they can't go on Oprah to cry about it.
"Wearing reptile skin is creepy and callous, and it makes her look even more out of touch. She and Lady GaGa seem so desperate to be freaks instead of recognised for their talents that you have to wonder if they realise that they are being laughed at."
Lady Gaga recently responded to PETA's attacks after she stepped out in a coat thought to be made of real fur, just shortly after they criticised her for wearing a wolf stole in a poster for Robert Rodriguez's new film, Machete Kills.
However, she refused to reveal whether the fur coat was real or not, and said while she respected the group's views, she expected it to be reciprocated.
"I am choosing not to comment on whether or not the furs I purchase are faux fur-pile or real because I would think it hypercritical not to acknowledge the python, ostrich, cow hide, leather, lamb, alligator, 'Kermit' and not to mention meat, that I have already worn," she joked.
> IN PICS: LADY GAGA'S CRAZIEST LOOKS
> WATCH: CATCH UP ON ALL TODAY'S CELEB GOSS
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