Female cop knocked out in Sydney brawl

Police have blamed alcohol for a brawl involving 20 youths in Sydney's south that resulted in four teenagers being charged and a female officer being knocked unconscious.

Officers say the fight, which broke out near a shopping mall in Cronulla on Wednesday night, was not race-related and involved only one group of people.

Miranda Local Area Command Superintendent Michael O'Toole says members of group were affected by alcohol.

"It was alcohol, kids and lack of respect for the public and police," he said on Thursday.

"And parents (needing to) take responsibility for their kids' behaviour."

Four teenagers, including a boy and girl aged 14, have been charged over the brawl.

Police said members of the group, who had come from Liverpool, had been "loud and abusive".

When police responded, a fight broke out as some of the group tried to free the 14-year-old boy who officers had approached.

A girl, 14, allegedly assaulted a policewoman, who was knocked unconscious and taken to hospital suffering a cut to her face and swelling to her eye.

The group then started fighting among each other, with some trying to restrain their friends from getting involved.

Officers used capsicum spray to break up the fight.

Police said the other brawlers were "moved on" by officers.