TV presenter Jamelia has said she was singled out by a fellow passenger to show a first class train ticket because she is "young and black".
The former Loose Women panellist and singer, 36, said she was in the first class carriage on a train with her 11-year-old daughter when she clashed with another traveller.
In a lengthy series of posts on Twitter, Jamelia said the unidentified female passenger was left as "red as a beetroot" when challenged.
Jamelia said her day had been ruined because somebody killed her "vibe".
She wrote: "So, I got on the train with my 11 year old daughter ... didn't even sit my bum on the seat good & a lady approaches me & asks me if I have a 1st class ticket.
"I look around. My daughter & I r the only black people in the packed carriage. I ask her 'why did you ask me that?'.
"She replies 'well I've just seen the conductor & he won't let you travel in this carriage'. I ask 'why?'. She says 'you need a 1st ticket'.
"I ask 'why have you assumed I don't have a 1st class ticket?' She says 'well, have you got one?'. I reply 'have you?'. She says 'yes I have'.
"I ask 'what made you ask that question to me and no one else?' She says 'it's because I wanted to sit with you, I just need to make sure'.
"I say 'I don't need a ticket for u to sit opposite me, no need to lie, my 11 year old could tell you why you asked, why not just be honest?'."
Jamelia said she told the woman "the least you could do is admit you were wrong to do so", to which she said the woman asked what she was implying.
She said: "I laugh, and say 'let's be honest, you've asked me because I look like young black girl & you've allowed your prejudice to speak for you'."
Jamelia said she laughed when the woman said she "would ask anyone I'm sitting with if they have a first class ticket".
She said: "I look her dead in the eye & say 'let this be a lesson to you, don't you ever make this assumption out loud again, I hope you feel ashamed'."
Jamelia and her daughter Tiana then moved, adding that a "white guy" who then sat in her seat was not challenged by the same woman.
She said: " My daughter looks over at the lady and says 'Are you not going to ask him for his credentials then?' The lady turned as red as a beetroot.
"I'm done not calling people out. I am also raising two wonderful young women who will grow up to call you out too ... you have been warned."
Last year, Jamelia said she was left scared for the safety of her children after she was racially abused by a man she believed was a police officer.
A representative for Jamelia has been contacted by the Press Association.