Amy Winehouse reacted with “deliberate and unjustifiable violence” when a dancer politely asked her for a photograph at a charity ball, a court heard today.

Lyall Thompson, prosecuting, said the 25-year-old singer appeared to be under the influence of alcohol or “some other substance” when she punched Sherene Flash in the eye at the summer ball in Berkeley Square, London, last September.

Winehouse, who performed at the ball before the alleged assault, denied punching Flash but admitted pushing her away when Flash put her arm round her.

The court heard the incident happened backstage in a dressing room soon after midnight on 26 September. Winehouse had agreed to have her photograph taken with Flash, whose friend Kieran Connelly then tried to get into the photograph.

Winehouse, who pleaded not guilty to assault at a previous hearing, said: “Her friend came round in front of us and started taking a picture … I was like, ‘Do I get a choice in this, hello?’

“I pushed her up, like away. I wanted her away from me. It was more like an indication of ‘leave me alone, I’m scared of you’. I meant to just get her away from me … I thought, people are mad these days, people are just rude and mad, or people can’t handle their drink.”

Winehouse said attention from the public was “not necessarily unwanted”.

Flash said she had had several alcoholic drinks that evening but denied being drunk. She said that Winehouse, who had drunk champagne, vodka and white wine, “punched forcefully in my right eye”, adding that she was shocked and began to cry.

The trial continues.