Sir Alex Ferguson 'refuses to believe' Chelsea side of story Manchester United and Chelsea were in a state of open warfare over the Mark Clattenburg affair last night, with Sir Alex Ferguson declaring that he is ready to testify in the referee's defence and that other managers should do so, in the firm belief that he will not be found guilty of racially abusing John Obi Mikel during last Sunday's match at Stamford Bridge. The Manchester United manager defended Clattenburg in the strongest possible terms yesterday, declaring that no official in the modern game would "stoop" to the kind of abuse that the Nigerian claimed after the game in which the official sent off two Chelsea players, and warned that the referee may never escape the stigma of the 25-year-old's accusation. Ferguson, whose side face Arsenal at Old Trafford this lunchtime, also reinforced the Arsenal manager Arsène Wenger's claim that Chelsea should have kept their incendiary complaints private. "I have had my run-ins with referees over the years, as you well know," Ferguson said. I have been fined a few times, but I just think that what has happened over the past week is unthinkable. It's an accusation which, even in the heat of the moment, shouldn't be made. You can't do that. Asked if he was prepared to stand up in Clattenburg's defence, should investigations by the Football Association and Metropolitan Police lead to action being taken against the 37-year-old, Ferguson said: "All of us." Ferguson attacked Chelsea, stating that "most people" would agree that the club should have allowed tempers to cool before going public on their claim against Clattenburg. Initial claims that Juan Mata was verbally abused by the referee have already been dropped. Wenger was careful on Thursday not to attack the substance of Chelsea's complaint - only the public way it was made - and Chelsea's manager, Roberto di Matteo, warned that the United manager's comments might backfire. He likes to talk about other clubs. We tend not to," Di Matteo said. We'll take into consideration what other people say and use it as a motivational tool for ourselves. United and Chelsea have history where claims of racial insults are concerned. The Old Trafford club's claims that a member of Chelsea's groundstaff, Sam Bethell, had racially abused Patrice Evra, were rejected by the Football Association in 2008 and the French defender was banned for four matches and fined £15,000 after the FA strongly criticised the reliability of United's evidence. But Ferguson, who said he had asked his players if they had heard Clattenburg abuse Chelsea players and said that they had heard nothing, declared the idea of a referee indulging in such abuse was beyond the bounds of belief. "I don't believe Mark Clattenburg would make any comments like that," he said. He said that it should be for the FA to decide whether Chelsea should be subjected to any punishment if the allegation proves unfounded. The latest twist in the racism in football story has led the Prime Minister, David Cameron, to declare that the FA should be doing more to tackle racism. That prompted Gary Neville, the England coach and Sky TV pundit, to take to Twitter to declare that the game was doing enough. Asked if the Conservative Party and Cameron were seeking to make cheap political capital, Ferguson said: "I think we are doing our best. There is a genuine drive to take racism out of our game. Unfortunately, we have had a couple of issues of race-related incidents, but when you look back over 25 years, there have been amazing improvements. You have to keep on progressing, bit by bit, to drive it out of the game completely. Ferguson's comments drew cynicism from some quarters and the United manager's relationship with Clattenburg has certainly not been as difficult as with most officials. Tottenham Hotspur were denied a victory at Old Trafford in January 2005 when Clattenburg ruled that Pedro Mendes' shot had not crossed the line. He also failed to spot Wayne Rooney's elbow at Wigan Athletic's James McCarthy last year and therefore did not dismiss the United striker. Ferguson said that Clattenburg had done Chelsea a favour by not issuing a red card to Fernando Torres for a high-footed tackle last Sunday. "When you think about it, Mark actually does them a favour because he should have sent Torres off in the first half," Ferguson said. By trying to keep a lid on it, on a combustible game, all these big games require good handling by the officials. But by sending him off for a second yellow card, Torres only misses one game, so he is free for the next two league games. They are not well endowed with strikers, Chelsea, so the referee has done them a favour. Those next two league games could be important to Chelsea's season - Torres might score the winner against Swansea this weekend. In a way Clattenburg has done them a favour.