The footage, which was given to local radio station Trent FM
A man was shown apparently being shot twice with a Taser gun by police in Nottingham in a mobile phone video taken by a bystander and posted on YouTube yesterday.
The footage has prompted calls from human rights groups for the Independent Police Complaints Commission (IPCC) to investigate the incident and review the use of Taser guns by police.
The video appears to show four officers converging on a man outside the city's Theatre Royal in an attempt to arrest him. When he resists, one of them tells the others to stand back and fires a Taser at him as he lies on the pavement. As the man continues to resist arrest, one of the officers punches the man in the head repeatedly.
Bystanders gather round and a policeman fires the Taser again at the man on the floor, while shouting: "Taser, Taser, Taser." The Taser gun consists of two darts on the end of wires containing a 50,000 volt electric shock.
The video was given to local radio station Trent FM and posted on YouTube, prompting more than 300 views and 100 comments within the first four hours.
Nottinghamshire police told the Press Association that officers were trying to arrest the 40-year-old man after they were called out by door staff at one of the city's nightspots; he was later charged on suspicion of causing grievous bodily harm.
Assistant Chief Constable Peter Davies said: "We understand that some members of the public may be concerned about this ... which is why we have referred this matter for an objective investigation to the IPCC."