Roberto Di Matteo has suggested that Sir Alex Ferguson should keep his views to himself over the Mark Clattenburg controversy while he added to the sense of friction between the pair by claiming that referees' decisions in the big games went in "one direction" in favour of Manchester United.

The Chelsea manager struggled to conceal his frustration at Ferguson's comments from earlier in the day, when his United counterpart had effectively questioned the veracity of the London club's allegation against Clattenburg. Chelsea accused the referee of racially abusing the midfielder Mikel John Obi in last Sunday's Premier League defeat by United at Stamford Bridge, and Ferguson said he could not believe that Clattenburg would have done so.

Di Matteo made it clear that he was unimpressed at Ferguson talking about a club other than his own, as he followed the Chelsea policy of not offering an opinion on the matter while Football Association and police investigations were continuing, and he agreed, when it was put to him, that Ferguson's remarks had been unhelpful. "Yes, and I have to say that it happened in the past as well," he said. "There is a lot of respect between your colleagues, the managers, in general. And everybody has a different approach. Some people talk about other clubs and clubs' issues and some don't. We'll take the knowledge of his comments but it doesn't mean that we share it.

"It's a free country where everybody has freedom of speech. We take into consideration what other people say and use it as a motivational tool for ourselves. It is a free country, as I say, and everybody can say what they want. He [Ferguson] likes to talk about other clubs; we tend not to. I'll leave it up to him."

Di Matteo and members of his Chelsea backroom staff clashed with Ferguson on the touchline during last Sunday's game, following Fernando Torres's second yellow card, for a dive, and again at full-time. Ferguson later said that Torres, the Chelsea striker, had no one to blame but himself after he "chose to go down". Di Matteo has maintained that Clattenburg's decision to send off Torres was wrong while replays showed that Javier Hernández's winning goal should have been disallowed for offside.

Di Matteo pointedly said he would "leave that up to you to judge", when he was asked whether it was fair for a manager of Ferguson's standing to use his influence via public comments and it seemed as though there was plenty that he might have liked to say. He gave vent, though, on the subject of refereeing decisions and he took a conspiratorial line over the notion that United have been favoured by them this season, notably in their league wins at Liverpool and Chelsea. United beat 10‑man Liverpool with the help of a debatable penalty.

"There is a lot of evidence for being concerned that all the decisions go in United's favour," Di Matteo said. "There are some feelings in general but I don't think they [referees] do that with a purpose. It's just part of their decision-making and it seems to go in one direction. Does it even itself out? I don't know.

"We need to support the referees. The players and managers have to do everything to support the referees. As much as it angers us and me personally when a key decision goes against me, I still believe we need to do everything to support the officials and make sure that they can perform at the best of their ability."

Chelsea are the European champions and Premier League leaders but they are a club under siege; Arsène Wenger, the Arsenal manager, has been another to criticise them for their handling of the Clattenburg affair and how they initially went "public with little proof". Di Matteo, though, claimed that Chelsea had conducted themselves properly. "We believe we did what was right," he said. "We believe we behave correctly. We have an objective in front of us and are going to continue to work for that. If other people have different objectives or opinions, it won't influence us."

Mikel will play at Swansea City on Saturday, with Di Matteo talking up the strength of his character, but David Luiz and Juan Mata have joined Frank Lampard on the injured list. John Terry serves the final match of his suspension, so Branislav Ivanovic will start in central defence.