The Football Association insist Tuesday's ticking off for Sir Alex Ferguson and Carlo Ancelotti should be "taken as a warning" by managers not to comment on referees before games.
Both managers made positive remarks about World Cup final referee Howard Webb ahead of their May 8 Barclays Premier League meeting between Manchester United and Chelsea at Old Trafford, contravening FA regulations which prohibit any comment - good or bad - about referees prior to games.
A FA statement said: "It was considered to be a minor breach, but a breach nevertheless, and it should be taken as a warning to all managers in the future that any such breach, even positive comments, are likely to result in a charge by The FA."
The governing body's regulatory commission warned United chief Ferguson as to his future conduct in relation to the comments before issuing an identical judgement on the Blues boss later on.
The statement added: "A Regulatory Commission has warned Sir Alex Ferguson as to his future conduct. Ferguson was charged with improper conduct, relating to his pre-match media comments made about match official Howard Webb on May 6, 2011.
"The chairman of the commission made the following statement following the hearing: 'This rule was brought in at the start of the 2009/10 season and this was reiterated formally to all Clubs again on 21 October 2010.
"This is a clear breach of the rule and it is the first time such a matter has been placed in front of a Commission.
"As a result of this charge the Commission were aware of other occasions where pre-match comments were made by other managers."
Ferguson is not believed to have offered a significant response to the charge.
Ferguson had said in the build-up to the match, which his side won 2-1: "We are getting the best referee, there is no doubt about that."