The Metropolitan Police Federation has said it is shocked by the results of its survey, which suggests the majority of officers feel unsafe working at the Notting Hill Carnival.
In a survey of 486 officers, 89% said they did not feel safe and 29% said they been assaulted while policing the event.
The federation, which represents rank and file officers, said the poll aimed to get "concrete evidence" of the experience of officers.
The carnival's organiser said the survey had an "an anti-carnival agenda" and only represented the views of a minority of the 7,000 officers who work at the event.
Notting Hill Carnival Ltd said the survey was "hugely flawed" as it returned the views of "at best just 7% of potential officers on duty".
The carnival - a celebration of Caribbean culture - takes place along a three-and-a-half mile (5.6km) route in north Kensington, west London, and has been running for more than 50 years.
'Like a warzone'
Simon Hill, deputy general secretary of the Metropolitan Police Federation, said:
"I'm actually quite shocked by some of the responses. I knew that the event wasn't popular, for a whole variety of reasons.
"But the candour from the officers and some of their descriptions of how they feel, how they felt at the carnival and their experiences of being assaulted, quite frankly were shocking."
The federation is also concerned the large scale of the event meant officers felt "powerless" to prevent those attending the event becoming victims of crime, Mr Hill said.
"No other event in London has this combination or level of issues for officers."
He said officers' concerns about long working hours also emerged from the survey.
'Anti-carnival agenda'
The event organiser said it condemned "all acts of violence" and said the results of the survey were "misleading".
"It is quite clearly written with an anti-carnival agenda that the police federation highlights every year. It is driven by unsubstantiated quotes and little solid data, designed to create negative headlines," Notting Hill Carnival Ltd said.
A spokesperson added that organisers rely on the collaboration with police and local authorities, but "this continued rhetoric unquestionably has a detrimental effect on the events planning process."
The Metropolitan Police's Deputy Assistant Commissioner Matt Ward said: "The views described in the survey "reflect many of the long-standing concerns about crowd safety and crime at Notting Hill Carnival.
"They also highlight recent positive changes to officer provision which we know we need to continue to build on."
He said the force was concerned by "unacceptable levels of crime at the event" and that "step change" was needed in the running of the event to prevent overcrowding.