"The police sergeant has been suspended from duty while inquiries continue.
"No members of the public were involved in the incident. The incident has been referred to the IPCC.
"Racism and racist language is totally unacceptable. The action taken in response to this allegation demonstrates the MPS's determination to act swiftly and to support those that challenge others when alleged racist language is used."
Last month Scotland Yard vowed to get to the bottom of "very damaging" footage of one officer apparently racially abusing a man and another allegedly assaulting a teenage boy last summer.
Since then a number of other allegations have surfaced against officers.
The Met is expected to have completed its investigations into the allegations by the end of this week.