Brian Coleman, the gay former Conservative London Assembly Member and ex-mayor of Barnet, has been arrested on suspicion of common assault.
The allegation relates to an incident that occurred in Finchley.
In a statement, the Metropolitan Police said a 51-year-old man was held on Thursday over an “alleged common assault”.
A spokesperson added the individual “Was taken to a central London police station and was subsequently bailed to attend a north London police station in late October pending further enquiries.”
Mr Coleman had been part of Mayor Boris Johnson’s team at City Hall until May of this year.
Mr Cole’s defeat meant he had to relinquish his position as chair of the London Fire and Emergency Planning Authority.
He is currently a Tory councillor in Totteridge.
Having served on the Greater London Assembly for 12 years, Mr Barnes was ousted as the member for Ealing and Hillingdon by Labour’s Onkar Sahota, a general practitioner in May.