Sir Alex Ferguson raised the temperature ahead of next weekend's crucial contest with Chelsea at Old Trafford when he claimed referees could be handing the Premier League title to the holders.
United's lead over Chelsea is now just three points, and should the Londoners win Sunday's match they would go top on goal difference.
With one eye on that game, Ferguson launched a trademark tirade at referees in general after yesterday's 1-0 defeat by Arsenal, and said he feared Chelsea will get a soft decision in next weekend's potential title decider.
Ferguson also noted that Chelsea were awarded a "ghost goal" against Tottenham Hotspur on Saturday even though Frank Lampard's shot did not cross the line, and Salomon Kalou also appeared to be offside before he scored their winner.
The abrasive Manchester United manager said: "Obviously, it gives Chelsea a major chance now and that's what happens. They got great decisions [on Saturday] for them. We never seem to get these kind of decisions. They seem to be getting them. They got one to win the league at Old Trafford last season so that's a worry."
His claims of a conspiracy theory made him sound like Jose Mourinho, who moaned that Barcelona get all the refereeing decisions following Real Madrid's 2-0 defeat last week. But Ferguson needs to be careful after he was given a five-match touchline ban in March for disparaging claims about referee Martin Atkinson.
For more than a year now Ferguson has been complaining that Chelsea get the big decisions when the two teams meet. He was unhappy about John Terry's winner at Stamford Bridge in November 2009, claimed Didier Drogba was offside before he scored the decisive goal in Chelsea's 2-1 victory at Old Trafford last April; and he incurred the five-game ban for questioning the integrity of Atkinson after he failed to dismiss Chelsea's David Luiz in their 2-1 victory in March. One oversight, however, is a blatant penalty that should have gone Chelsea's way when Ramires was fouled by Patrice Evra in last month's Champions League quarter-final first leg at Stamford Bridge.
The United manager was disgruntled his team had not been awarded a late penalty yesterday when Michael Owen was caught by Gaël Clichy, but he played down the blatant handball in the first half by Nemanja Vidic that was also missed by the match officials.
"I've seen the two incidents. The first one was a definite flick of the hand from Vidic but it's very difficult to see that one," Ferguson told Sky. "But we all had a clear view of the second one. It was a clear penalty kick. We're not going to get decisions like that in a major game. They are too big a game. We don't seem to get these decisions.
"It balances out in that respect but I think it was difficult to see that one [Vidic's handball] – [Robin] Van Persie was the only one who complained. But the one at the end, Clichy knew, he put his hands up in horror."
Aaron Ramsey decided the match when he applied a simple finish to a flowing counter-attack in the 56th minute, with his first goal for Arsenal since his leg was broken in two places in February 2010 by Stoke City's Ryan Shawcross.
The Arsenal manager Arsène Wenger said: "I am very happy for Ramsey, when you think his incident happened 14 months ago and only now he looks just to be back to his best."
Van Persie rubbed salt in United's wounds by questioning their desire. "In the end I think we played better. We wanted it more. They played just on the counter-attack so in the end, I think, a fair result," he said.
Arsenal were without captain Cesc Fabregas, who was ruled out with a thigh injury he had picked up during a training session on Saturday. In addition Samir Nasri, with a hamstring injury, did not return for the second half.
Wenger said: "Samir has a small hamstring problem, Cesc has a kick on his thigh that disrupted some fibres. We will know on Tuesday if he can practise again. Cesc has a chance to play on Sunday."
Schalke crash to Bayern
* Schalke prepared for Wednesday's Champions League semi-final second leg trip to Manchester United with a 4-1 defeat at Bayern Munich on Saturday. Arjen Robben's sixth-minute opener was cancelled out by a Holger Badstuber own goal before goals from Thomas Müller and Mario Gomez put Bayern 3-1 ahead after 19 minutes, Müller later adding his second.