Brighton and Hove Council has defended the number of stewards deployed at the Big Beach Boutique gig, which drew a crowd of 250,000.
A total of 260 stewards were on duty at the Fatboy Slim show - one for every 961 partygoers.
The party's organisers, production company Big Beach Boutique and Brighton and Hove City Council, believed they had sufficient guards to cope with the estimated 60,000 visitors, 20,000 more than attended last year's event.
But on the night, a human tide poured on to the seafront, swamping the beach and blocking roads.
A council spokesman said the Safety Action Group (SAG), set up to oversee numbers and crowd control, conducted a full risk assessment.
Guidelines from the Health and Safety Executive have previously recommended a ratio of one steward to 100 people for similar events.
The council said the equation was not relevant for an unticketed free event and its numbers were drawn from the most recent guide, which based the number needed on a full risk assessment, not a formula.
The spokesman said: "The SAG arrived at a figure of 260 based on the expected turn-out.
"Following last year's highly successful event, the council planned for an estimated 60,000, a figure arrived at in consultation with all parties, including emergency services.
"It was thought to be a well-planned and successful event, based on the previous year."
The SAG, made up of representatives of all the emergency services and the council, met regularly in the run-up to the concert.
The spokesman said: "The arrangements that were made for the event were carefully thought through and had the backing of all the emergency services, the council and the organisers."
Most of the stewards, crowd control and security staff came from Brighton-based Select Security.
Operations director Anne-Marie Chebib said: "We were employed by the production company but are still undergoing a critical incident debriefing so I cannot say any more.
"We are not running and hiding - my staff did an amazing job."
The Health and Safety Executive said free events were notoriously difficult to regulate.
A spokeswoman said: "Because it is free, there is no way of knowing how many people will turn up.
"It is up to the organisers of the event, with input from the local authority, to arrange adequate cover."
The event's promoter was Alex Poots.
At his office, producer Jo Paton refused to talk to us about how and why the concert had been promoted on TV, radio and in the Press.
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