The Portuguese believes his two rivals do not have to worry about world record transfer fees as they are not top clubs in the same bracket as the Red Devils
Jose Mourinho used Paul Pogba's unveiling as a Manchester United player to once again take a swipe at his Premier League rivals.
United finally confirmed the capture of Pogba this week, having parted with a world-record fee to bring the Frenchman back to Old Trafford from Juventus.
Liverpool boss Jurgen Klopp raised doubts over the move - which could be worth as much as €110 million - while Mourinho's long-term rival Arsene Wenger branded the deal "completely crazy".
Mourinho said the pair's comments were "not ethical" last week, and used an interview with United's in-house TV station MUTV to once again belittle Liverpool and Arsenal.
He said: "I know the discussion, I understand that, sometimes in football, things happen and the club breaks the record, but this is only possible at clubs like Man United.
"When I heard some of the comments and heard some of the managers criticising that, I don't think they ever have this problem because, to have this problem, you need to be at one of the top clubs in the world. So at Man United it can happen."
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Turning attentions to his latest recruit, Mourinho was lavish in his praise of a player who left United on a Bosman move for Turin four years ago.
"He's a very young player, an unbelievable midfield player with such physicality but, at the same time, such agility, co-ordination, skill," Mourinho added.
"He has everything. What he has to learn now is how to play with us because I always say that in football you can be a super player, like he is, but a team is a team and you need to learn how to play in the team, and the team needs to learn how to play with you.
"We need to get the best out of him and this will be a process. So if he needs protection, I am here to protect.
"I know some people think that he arrives here now and, the first time he touches the ball, he scores, but I'm here to protect him and give him the best conditions to be what we think he is going to be, which is a football player for Man United, a reference for this club. I'm so happy."