The star's pal, designer Stella McCartney, said she went mad when she saw Madonna wearing the item.
Animal rights people claim lambskin coats are often made from the fur of unborn lambs.
Caught out
Stella said Madonna insisted she never wears anything that she doesn't eat.
"It's like wet curls. So I said, 'I didn't know you ate foetuses,' and she was like, 'Eeew!' I haven't seen her in it since."
The designer claimed she'd also caught out another pal, actress Gwyneth Paltrow, wearing real fur trim on a jacket.
"I love her, but on the fur thing, people really are very fickle," Stella said.
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