A Metropolitan Police inspector has been arrested on suspicion of racial abuse, the force said.
The officer, who is based in north London, is being investigated by the force's Directorate of Professional Standards (DPS) and the Independent Police Complaints Commission (IPCC) after an incident in Barnet, north London, on Monday.
A Metropolitan Police spokesman said the officer, who was off-duty at the time of the alleged incident at 7.40am, was arrested by the DPS the following day and has been suspended while the incident is investigated.
"The male officer was arrested on suspicion of a Section 4 Public Order Act offence (racially aggravated words or behaviour likely to cause harassment, alarm or distress)," a spokesman said.
"He is at present on police bail and has been suspended from duties pending the outcome of the criminal investigation."
The IPCC confirmed it was supervising the DPS investigation, which is the latest allegation of racism by Met officers under investigation by Scotland Yard and the IPCC.
They include the case of Pc Alex MacFarlane, 52, who will face criminal charges after being accused of racially abusing a suspect during last summer's riots.
The alleged incident was recorded on a mobile phone. He will appear before magistrates in May charged with a public order offence.
Last week, black firefighter Edric Kennedy-Macfoy, 28, claimed he was assaulted and Tasered by a group of police officers because of his skin colour.
Mr Kennedy-Macfoy, who has lodged an official complaint, also said he was insulted and arrested without good cause when he went to assist the six policemen while off-duty as they were dealing with a disturbance last September.