A fresh investigation into police conduct during the G20 protests was launched tonight after video footage showed an officer hitting out at a woman during the summit.
Footage which appeared on the website YouTube showed an officer swiping at the female with his hand before apparently hitting her across the legs with a baton.
Scotland Yard said it was in the process of referring evidence to the Independent Police Complaints Commission, which launched an inquiry last week into the death of Ian Tomlinson.
A Metropolitan Police spokesman said the matter raised "immediate concerns''.
He said: “Once we were notified of this footage by a media agency this afternoon, we began to take steps to identify this officer and are currently in the process of referring the incident to the IPCC.
“Every officer is accountable under law, and fully aware of the scrutiny that their actions can be held open to. The decision to use force is made by the individual police officer, and they must account for that.”
Earlier the IPCC said it remained hopeful that fresh CCTV footage would help piece together Mr Tomlinson’s final moments.
Investigators are trying to trace the 47-year-old newspaper seller’s movements around the fringes of angry demonstrations outside the Bank of England.
Mr Tomlinson collapsed and died from a heart attack after clashing with police officers at least once as he walked home across the City.
A Metropolitan Police constable caught on camera hitting Mr Tomlinson with a baton and pushing him to the ground has been suspended from duty.
A spokeswoman for the IPCC said there are a number of public and private CCTV cameras in the streets around where Mr Tomlinson died.
She said an earlier statement by the watchdog’s chairman Nick Hardwick that “there is no CCTV footage” may not be accurate as investigators continue to trawl through hours of evidence.
The spokesman said: “From the outset it has been a main line of our inquiry to recover all CCTV from the Corporation of London and from all private premises in the area.
“This work is ongoing and involves many hours of viewing and detailed analysis.”
Mr Tomlinson died as more than 5,000 protesters converged on the City of London on April 1 to mark the G20 summit in Docklands.
Amateur video footage captured by a New York fund manager emerged several days later of him being pushed to the ground by a policeman.
Other photographs have also come to light of Mr Tomlinson apparently remonstrating with officers in a riot van in Lombard Street up to an hour earlier.
Commissioner Paul Stephenson said the images of Mr Tomlinson being struck “raised obvious concerns” as questions arose over the police tactic of “kettling” demonstrators – penning them in – to prevent them moving freely.