A complaint by the family of a man who died during the G20 protest is to be investigated by the Independent Police Complaints Commission (IPCC).
Ian Tomlinson died after an incident during clashes at a meeting in London of political leaders on 1 April.
The complaint alleges an acting detective inspector gave incorrect information to a pathologist at a post-mortem examination on Mr Tomlinson, 47.
The IPCC is already probing the death and police information given to media.
Mr Tomlinson's stepson Paul King described the family's complaint at a candlelit vigil for the newspaper seller on Tuesday night.
He alleged the unnamed officer told the pathologist at a third post-mortem examination on Mr Tomlinson that he had fallen to the ground.
Mr Tomlinson, who was not involved in the G20 protest, was allegedly struck by an officer and pushed to the ground.
A member of the Met's territorial support group was suspended and questioned on suspicion of manslaughter over Mr Tomlinson's death.
He was caught by an amateur cameraman apparently pushing Mr Tomlinson to the ground.
A file was passed to the Crown Prosecution Service at the beginning of August by the IPCC.