Kelis has accused Britain of being "racially decades behind progression" after she was allegedly subjected to abuse at an airport because of her skin colour.
Using her Twitter account, the American singer claimed she was accused of queue-jumping by a "red faced sweaty man" who called her a "slave" and "probably a disgusting Nigerian" and told her to call him "Sir".
Kelis said that man labelled her "Kunta Kinte" - the name of a slave in Alex Haley's book Roots - and "ranted and raved some more".
She claimed an official behind the passport desk had laughed, shaken his head and said "Kunta Kinte".
The music star, who did not name the airport, added: "All the while the entire line full of people I just sat on a plane with for almost three hours, over 50 people said nothing. Didn't flinch."
The incident apparently took place as the 32-year-old was travelling home after performing at Bestival on the Isle of Wight.
Kelis tweeted: "I didn't say anything at the time of the riots in London for a lot of reasons. But I am in London all the time and today I'm gonna say that the racial issues in the UK are disgusting. It's racially decades behind progression because everything is swept under the rug. People don't talk about it. People don't fight about it."
She said her own country was "the poster child for racial inequality", but that it was not a secret.
Kelis, whose hits include Milkshake and Caught Out There, claimed she had not lost her temper at the airport because she had her two-year-old son with her.
The UK Border Agency was unavailable for comment.