A still from the video.
A still from the video.
New South Wales police will conduct an investigation after being accused of using excessive force during last weekend's Mardi Gras.

A video apparently shot at this weekend's Mardi Gras shows an unidentified reveller in handcuffs being thrown to the ground by a policeman, who then stands on the man's back.

The footage does not show clearly what happened immediately before the man is thrown to the ground.

Police said an 18-year-old man had been issued with a field court notice for the offences of assaulting police, resisting arrest and using offensive language following an incident at the intersection of Riley Street and Oxford Street in Surry Hills on Mardi Gras night.

"Following vision of the event being made available to police, an internal investigation will be launched to determine the full circumstances leading up to and surrounding the incident," a police spokesman said.

The 18-year-old man is due to appear in Downing Centre Local Court on April 1.

Another man has claimed that police handled him roughly during Mardi Gras celebrations. Leaders in the gay community have expressed concern.

"I'll be calling for an investigation," said the state MP for Sydney, Alex Greenwich. "From what we can see it does appear to be heavy handed and extremely concerning."

The video was uploaded by an account called SydneyMardiGras2013 which claims the footage was shot near Oxford Street about 11:30 pm on Saturday.

Onlookers in the video can be heard protesting and alleging the man had been handled violently before the video started rolling. "We just saw you whack his head against the ground," a woman can be heard to say. "His blood is on the ground".

Another police officer instructs the person behind the camera to "stop filming, mate". When asked why, the officer responds: "Cos I said".

The chair of this year's Mardi Gras, Peter Urmson, said he would seek a meeting with police. "I've just seen the video myself and obviously have grave concerns," he said. "We're not gonna let this get swept under the carpet".

Another gay activist spoke to Fairfax Media and alleged that up to five police held him down and kicked him, after he ignored their instructions to not cross a road.

"I was kicked several times," he said. "I was handcuffed and had my face pushed into the ground.

"I had a police officer leaning on me. I told him I couldn't breathe. He said, 'If you can talk you can breathe".

The state MP for Sydney, Mr Greenwich, MLA said he knew the man and was concerned by his account.

"He is someone who I would believe: that's based on the fact that he's worked with the police very closely when organising major gay and lesbian rights rallies," he said.

Mr Greenwich said he intended to raise the issue with the Police Minister and police directly.

"In previous years the police have done a really good job partnering with the parade," he said.

Raw Video: A man is detained by NSW Police at the Sydney Mardi Gras 2013.