A woman who was filmed being struck by a police sergeant at the G20 protests has described his actions as "very violent and unnecessary".
Film footage showed an officer hitting Nicola Fisher, 35, from Brighton, across the face with his hand and on her leg with a baton.
"He just said 'get back', pushed me and then hit me across the face," she said.
Ms Fisher admits pushing the officer. The Independent Police Complaints Commission (IPCC) is investigating.
The sergeant accused of striking Ms Fisher works for the Territorial Support Group and has been suspended from duty pending the IPCC inquiry.
Ms Fisher, who is being represented by PR agent Max Clifford, was making her way to a vigil for 47-year-old Ian Tomlinson who died during the 1 April G20 protests.
'Angry and shocked'
She told BBC South East Today that at first the protest seemed "very calm and very peaceful".
"Suddenly quite a few police officers came and made a line in front of us and almost straight away the officer in front of me shouted 'get back' and pushed me before I even had a chance to move.
"When he did that I, as an instant reaction, pushed back, then straight away he gave me a back hander across my left cheek."
Ms Fisher said she reacted by swearing at the officer.
"I started shouting at him saying 'what are you doing hitting a woman?' and pointed at my face and said 'do you realise there are three film crews filming you?'.
"I was just so angry and shocked that he had done it and to be honest, I really didn't think he was going to get his baton out and hit me like he did.
"It wasn't a tap, he used his full force. It was very violent and aggressive and unnecessary."
Ms Fisher added: "If he had wanted me to move he could have asked me politely or he could have just picked me up and moved me.
"There was no need to do any of that."
She said a number of men witnessed the incident and scuffles broke out between the men and some of the officers.
After footage of the incident came to light the Metropolitan Police issued a statement saying the actions of the officer raised "immediate concerns".
The IPCC said a total of 145 complaints had been made following clashes between police and protesters at the G20 summit in London.
Former London mayor Ken Livingstone said that following media reports there might be violence at the G20 protests, the police then "responded with this ridiculous 'we're up for it'."
He also said that the police tactic of "kettling" - coralling protesters into a confined space for a number of hours - should only be used as a last resort.
"Police need to accept that people have a right to protest," he added.
A policeman has been interviewed under caution on suspicion of the manslaughter of Mr Tomlinson after a second post-mortem examination appeared to show he died of abdominal bleeding, not a heart attack as first thought.
Mr Tomlinson was struck and pushed over by an officer during protests on 1 April in the City.
Referring to the death of Mr Tomlinson, the ex-mayor said: "Poor Mr Tomlinson was just trying to get home, he kept running into one barrier after another, and eventually it cost him his life."
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