The Royal family found themselves caught up in a new race row today after it emerged the Prince of Wales has been calling an Asian friend by the nickname "Sooty".
Charles has been referring to Kolin Dhillon by the moniker for years whenever they meet at Cirencester Polo club where they are both members, according to a source.
Princes William and Harry also play at the club, which is close to their father's Highgrove estate in Gloucestershire, but the source was not aware of the young royals using the nickname.
The development comes a few days after Harry was widely condemned for calling a former Army colleague "Paki".
Prime Minister Gordon Brown branded the comment unacceptable and the Prince, an officer in the Household Cavalry Regiment, faces a dressing down from his commanding officer.
The source said Mr Dhillon was "comfortable" with the nickname which Charles uses but when William and Harry were boys they referred to the player by his surname and Christian name.
The use of the word is at odds with Charles' interest in Britain's wide ranging ethnic minority community and his championing of inter-faith dialogue.
Graham Smith, campaign manager for the organisation Republic, said: "I think it goes to show the royal family are not a symbol of unity, it's not something we can rally around, they're quite divisive.
"People are saying they are not racist but on the evidence in the public domain I think that's to the contrary.
"It also shows how hugely out of touch they are and that they live in a very isolated world, only mixing with a certain kind of person."
Harry was caught on film three years ago referring to former Pakistani platoon member Ahmed Raza Khan as "our little Paki friend".
A St James' Palace spokesman said the 24-year-old Prince was "extremely sorry" for the comment and stressed that he had been speaking to a friend without malice.
But the soldier's father, Muhammad Yaqoob Khan Abbasi, has accused Harry, who is third in line to the throne, of using a "hate word" against his son.
The Sun newspaper reported that the Prince had personally apologised to his former Army colleague but St James' Palace would not comment on the article.
When asked about Charles' use of the nickname Sooty both Clarence House and Cirencester Polo Club declined to comment.
The Telegraph newspaper's Mandrake column first reported that Charles had been calling Mr Dhillon Sooty, but it also quoted an anonymous Cirencester polo club member as saying William and Harry also used the nickname.
Clarence House later issued a statement which said: "We are not going to comment about a nickname which allegedly is used in a particular club.
"To imply the Princes are racist is ridiculous. Through their charity work all three of them are committed to helping people both in the UK and abroad regardless of who they are."