Sir Alex Ferguson was involved in a furious half-time altercation with referee Steve Bennett as Manchester United crashed to a sorry 3-1 derby-day defeat at Eastlands.
Ferguson let fly with a verbal tirade at Bennett as he lashed out at the Orpington official's handling of a shocking defeat which left any chance of a Premiership title challenge in tatters.
The United boss was particularly annoyed by a Stephen Jordan tackle on Wayne Rooney, which saw the City man rake his studs down the striker's shin which went completely unpunished.
But claims that Ferguson had called Bennett `a cheat' and insinuated he would need a police escort to get out of the stadium have been strongly denied by United.
United officials attempted to clarify the situation this evening, accepting an altercation took place but denying Ferguson strayed away from Bennett's on-field performance.
'There was a heated exchange but the content was limited to the manager's assessment of the referee's first-half performance,' said a United spokesman, who has received Ferguson's version of events. 'But any talk of a threat is nonsense.'
If Bennett decides to include the incident in his post-match report Ferguson could find himself in trouble with the Football Association.
Ironically, Bennett was not even supposed to be in charge of today's encounter but stepped in to replace the injured Mark Halsey.
But his failure to protect Rooney, instead booking the striker for dissent as he registered his complaint at Jordan's tackle, and the decision to allow Trevor Sinclair's 30th-minute opener, even though the former England man appeared to be offside, caused Ferguson to erupt.
'In games like this, you need the referee and linesmen to be strong but we didn't get that,' said Ferguson, whose temper was tested even further by the second-half dismissal of Cristiano Ronaldo for a woeful lunge at Andy Cole moments after the Portugal winger had been chopped down by Jordan.
'It was very disappointing,' said the United chief.
'He did not get a foul for the bad tackle just before and was probably frustrated. But it was more rash than vicious. He didn't touch the player, in fact he didn't get anywhere near him, yet the referee decided it was a red card. Maybe he should look at it again.
'The problem is interpretation. On Wednesday, Wayne Rooney got caught by a knee high tackle yet there wasn't even a booking. Every referee is different and we know Steve Bennett, we know him.'
Even City boss Stuart Pearce claimed Ronaldo was unfortunate to be sent off, with the Portugal winger set to miss Wednesday's FA Cup replay with Burton, Sunday's Premiership encounter with Liverpool and the Carling Cup return against Blackburn unless Bennett revises his opinion.
'It didn't look like a poor challenge and I didn't think it was a sending off,' admitted Pearce.
Ferguson's frustrations mirrored that of his team, who for the third time in four years were humbled at the home of the fierce local rivals, deservedly beaten by a side showing greater hunger and desire.
Pearce admitted he borrowed an old trick from Ferguson in an effort to galvanise City, who he felt were not given due credit in the build-up.
'When people were talking about the game this week, it was as though we were Burton Albion,' he said.
'We are not Burton Albion. We have some great international players in our side. If we are on all firing on all cylinders we can beat anyone on any given day.
'Manchester United are a great club, one of the best in the world. They have the ability to spend £5million to bring in cover at left-back. That might be my entire transfer budget, which puts this result into perspective.'
Not even Ferguson could deny City their win. Once he had sidestepped his dispute with Bennett, the Scot cited weak defending and a lack of cutting edge in the final third as the major reasons for United's demise.
Throw in an ineffective midfield and Ronaldo's dismissal, it is hard to see how the visitors' performance could have been much worse.
Ferguson was left to reflect on the loss of an 11-game unbeaten league run and a major selection decision he seemed to get badly wrong.
In offering £5million new-boy Patrice Evra his debut at left-back, Ferguson was taking a risk anyway, but by drafting Mikael Silvestre in to chaperone his fellow Frenchman, he weakened his defence too much.
Evra never looked comfortable and was replaced at half-time, while Silvestre's blunder gifted Darius Vassell City's second.
'Maybe it was a bit of a gamble playing Patrice,' said Ferguson. 'I took him off because at 2-0 down I wanted to make sure we didn't lose any more goals and John O'Shea has more experience of derby games.
'I am not singling anyone out. The defending was poor and that is what has cost us the game.'
United's chances of snatching at least a point were not entirely ended by Ronaldo's departure as Ruud van Nistelrooy did pull a goal back with his 18th of the season.
But in their desperation to grab an equaliser, United left themselves wide open at the back and Robbie Fowler finished them off in stoppage time.
'When they went down to 10 men, it seemed like they had 12, so there was a sense of relief at the end,' said Pearce.
'After the disappointing time at Christmas, this was a very important result for us and hopefully it will kick-start our season.'
Richard Dunne hobbled off in the second-half with a knee injury and will be sent for a scan with rumours already circulating that he has suffered season-ending cruciate damage.
'We won't be sure until we see the results of the scan,' said Pearce. 'He is suffering from some sort of knee damage but hopefully it is not as bad as it might be.'