The Mayor is considering moving the authority that oversees Scotland Yard to new offices in City Hall.
The proposed move of the Metropolitan Police Authority would coincide with Boris Johnson taking over as its chairman and be symbolic of his tightening grip on London policing.
The authority's current headquarters are in Dean Farrar Street, St James's Park, a street away from Scotland Yard.
With Mr Johnson's increasing workload and the MPA's current offices, which house around 100 staff, being deemed "unsatisfactory", a move to City Hall is regarded as highly likely.
But a senior MPA member today warned the move could result in job cuts at City Hall, which is already overcrowded with more than 600 staff in a building designed for around 400.
Green member Jenny Jones said: "Moving the Metropolitan Police Authority into City Hall might make the Mayor's life easier when he takes over chairing the authority, but without significant job cuts there just isn't the space to accommodate the authority's staff."
The MPA has leased its present offices since July 2002 and before that it was located with the London Assembly in Marsham Street.
Former MPA member Tony Arbour said the move spoke volumes about the Mayor's role chairing the authority.
"It makes a statement to the police that they are responsible to the Mayor rather than just a police authority," Mr Arbour said. "There is an obvious advantage."
Kit Malthouse, deputy mayor for policing, said: "The Metropolitan Police Authority's current offices are unsatisfactory for a number of reasons so it is right to consider alternatives, but no decisions have been taken yet."
