Alleged incident comes after singer faced backlash over visit to Calais migrant camp
Lily Allen said she was turned away from a black cab after being told to "find an immigrant" to give her and her daughters a ride.
The London-born pop star wrote on Twitter she "had a glimpse of what it feels like to be discriminated" after being shunned by the driver.
"Just tried to get in a black cab with my kids," Allen wrote.
"The driver looked at me and said, 'find an immigrant to drive you, you stupid tart'."
The alleged interaction comes after the singer suffered a public backlash for comments she made during a visit to the Calais migrant camp.
Allen visited the Jungle earlier this month, where she appeared in a BBC video talking to a 13-year old boy from Afghanistan.
In the video, Allen tells the boy: "I apologise on behalf of my country. I'm sorry for what we've put you through."
Her comments caused a stir on Twitter, with many users criticising the star for speaking on behalf of the country.
Allen got a similar response on Friday after her alleged black cab interaction.
Having lived a life of privilege, that interaction has given me a tiny glimpse of what it feels like to be discriminated against.— lily allen (@lilyallen) October 28, 2016
One Twitter user asked Allen to post the vehicle's registration to prove it had happened.
"I had both my hands full with children," she replied. "Couldn't get to my phone fast enough."
She responded to another person who said that it "definitely didn't happen", writing that they were "victim shaming" her.
In another post, the 31-year-old added: "Having lived a life of privilege, that interaction has given me a tiny glimpse of what it feels like to be discriminated against.
"There is so much work to be done. But we can do it. Let's stamp out this stupid horrible ignorance together," she wrote, followed by #takeourcountryback.