The royal, who is married to the Queen’s cousin Prince Michael, proudly sported the brooch on her coat as she was driven into Buckingham Palace on Wednesday.
Blackamoor is a style of artwork dating from the 18th century that is usually found in sculpture, jewelry and textiles in which black men and women are often depicted as slaves.
The royal lunch would have been the first time Princess Michael met Prince Harry‘s biracial fiancée, Meghan Markle.
The American actress’s mom, Doria Ragland, is black and has often spoken of racism she experienced as a child and as an adult.
Outraged social media users slammed the royal for her choice in jewelry.
One said: “Has no-one noticed the blackamoor pin that Princess Michael of Kent is wearing? Really? Meghan Markle official meets the family and is greeted by THIS?”
Another took aim at her “racist jewelry” while a third added: “I hope the Queen is going to ban this racist, horrible woman from any further gatherings. This woman is an embarrassment to the Royal Family.”
It’s not the first time the royal — dubbed Princess Pushy — has been embroiled in a racial storm.
She strongly denied the claims and said she would be “ready to go back to the colonies” during the dispute with the table.
Markle has spoken out about racism after being subjected to years of prejudice by people unaware of her heritage.
She claimed that some who believed she was white made distasteful “black jokes” in front of her, and she revealed her hurt when someone called her mom “the N-word” when she was pulling out of a parking space.
She said: “My skin rushed with heat as I looked to my mom. Her eyes welling with hateful tears, I could only breathe out a whisper of words, so hushed they were barely audible: ‘It’s OK, Mommy.’”