An "isolated" police officer was "dragged" into a crowd before being stamped and kicked on during a riot in Bristol.
Avon and Somerset officers are said to have been in "fear for their lives" as violence broke out following a Kill The Bill protest on Sunday 21 March.
One officer suffered a punctured lung while others were left with broken bones.
Chair of Avon and Somerset Police Federation Andy Roebuck told ITV News West Country: "We had some real, horrible violence towards our Bristol police yesterday evening. It was horrendous.
"We've been speaking with a number of these officers and a couple of them have actually said that they were in fear for their lives.
"This is the magnitude of the violence and hatred that was directed to our police officers.
"Our officers have the right to do their work to the best of their capability and return to their families fit and well."
He said at one point a "slightly isolated" officer was "dragged" into the crowd, adding: "And then we had about 10 or 12 of them actually stamping and kicking that officer while he was trying to defend himself on the floor."
Seven arrests have been made so far, and Avon and Somerset Police have said there will be "serious consequences" for those involved.
But some of the people there claim they were met with a "disproportionate" response from police.
People who spoke to ITV News West Country at the scene said physical retaliations from civilians were a direct response to antagonising actions from officers.
One woman claimed her friend had pepper spray used on her by a police officer when she was only "trying to have a conversation".
She said: "It's completely disproportionate and it's genuinely disgusting."
Demonstrators speak to ITV News West Country
One man said: "We are not aggressive people. When people are coming at us, battoning us, pepper spraying us, what are we going to do? It's in our human nature to retaliate and attack."
Another man said: "When you make peaceful protest illegal, you make violent protest inevitable."
The violence has been widely condemned, with Chief Constable Andy Marsh saying it was caused by a minority who descended on the event "looking for an excuse to commit disorder".
Watch Andy Marsh's interview with ITV News West Country
Chief Constable Marsh said there was "no prior intelligence" to indicate violence would be committed on such a scale.
He said: "The people involved in this were just looking for violence and the opportunity to create disorder. They should be ashamed of themselves. They’re an absolute disgrace and they do not represent Bristol."
Bristol Mayor Marvin Rees said the rioters had brought a "shameful day" on the city.
He said the disorder would be used to justify the legislation, adding: "I draw a hard line between those people out smashing up my city yesterday and the Bill. They have got nothing to do with the Bill.
"I would imagine, and I think experience would suggest, that there are a group of people running around the country looking for any opportunity to enter into physical conflict with the police or representatives of what they see is the Establishment."