An incident in which an English woman was struck in the face by a police officer during G20 protest clashes will be independently investigated, it has been confirmed.
The actions of the territorial support group sergeant outside the Bank of England will be examined by officials at the Independent Police Complaints Commission (IPCC).
However, a spokesman said the Brighton woman, known only as Nicky, has yet to come forward to make a formal complaint about the alleged assault on April 2.
Deborah Glass, of the IPCC, said the watchdog will investigate after the matter was referred to them by senior officers at the Metropolitan Police.
She said: "It is appropriate to use our own investigators to deal with this latest incident arising from the policing operation relating to the G20 Summit. I have taken this decision bearing in mind the death of Ian Tomlinson and the volume of complaints made by the public about the actions and tactics of the police service during the policing of the G20 demonstrations."
Earlier, the sister of the protester who was slapped across the face by a police officer said she had been left "traumatised".
Natalie Thompson said she hopes to take the case against the police sergeant as far as possible and has taken photographs of her injuries.
She told London's Evening Standard: "My sister was terrified after the attack and very traumatised. She did not want to come forward earlier because she feared nothing would be done but once the footage was released on the internet, she decided to do something about it."
The Metropolitan Police suspended the territorial support group officer on Tuesday night after a video of the incident was posted on YouTube. Another officer from the unit has already been suspended over the death of newspaper seller Ian Tomlinson, who died from a heart attack minutes after being hit with a baton and shoved to the ground.
The woman was in a crowd of more than 100 people attending a vigil for Mr Tomlinson who were encircled by police outside the Bank of England for several hours on April 2.
Amateur footage shows the woman shouting at police before an officer wearing body armour hits her across the face with the back of his hand.