West Ham co-owner David Sullivan has claimed an agent threatened physical violence against him and one of his players during the transfer window.
QPR manager Harry Redknapp described agents' behaviour as like "gang warfare" and Sullivan echoed his sentiment.
The 63-year-old told the Daily Mail: "In this window I have had an agent threaten me and one of our West Ham players with physical violence because he thought he was being cut out of a deal.
"I heard of three or four agents trying to jump in on other deals. Some of these people are like scavengers. It was all deeply unpleasant and I'm glad it is over. Now we can get on with the football."
Redknapp had earlier warned of agents' behaviour when he said: "Every agent seems to be trying to screw each other. It is like gang warfare out there. It is scary."
He added: "It is unreal. It is unbelievable what is going on. They're all fighting for big money - that is the problem."
Sullivan offered a similar view, saying financial demands from agents had got out of control and the FA needed to create legislation to cap agent's fees.
"We are talking millions of pounds here around a transfer. There are too many agents and not enough transfers to feed them," he said. "Agents who would once demand £50,000 for their part in a transfer now want £500,000 to £1 million to either bring a player or keep a player. It is quite outrageous.
"The FA should cap the amount paid to agents for their work."
The West Ham co-owner told of one agent who took representation of a player for a single day and demanded to be paid up to £1.5 million for his part in the negotiations.
He went on to express his admiration for West Brom chairman Jeremy Peace after the Baggies refused to sell Peter Odemwingie despite the player going AWOL on deadline day to force a move to QPR.
He said: "His player, Peter Odemwingie, drove down to QPR and was actively trying to force a transfer, but Mr Peace refused to cave in. He held his ground. He would not be bullied.
"You cannot give in to players like this. It is the same as giving in to terrorists or kidnappers. If you pay the ransom, they will only come back for more."