Wolves head coach Nuno Espirito Santo has refused to apologise for his criticism of Lee Mason, after claiming the referee does not have the "quality" to be a Premier League official.
Nuno expressed his frustration with Mason's performance following Wolves' 2-1 defeat at Burnley on Monday.
The Football Association has sought observations from the Portuguese, who has confirmed he will submit his response on December 29.
"I think I should apologise for the timing of my comments, probably they were not at the best moment to come across because sometimes bad interpretations can come of it," said Nuno, speaking ahead of Sunday's match against Tottenham, live on Sky Sports.
"For that, I will apologise for my timing. But I will not apologise for my words and my thoughts."
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Nuno insists he has never questioned the integrity of referees during his managerial career.
"I never did it, will probably never do it in my life, but what I said is about the ability of the referee," he added.
"What I felt and what I saw in the match and previous matches.
"We expect high levels of performance, high standards. As managers, as players, we always want to improve.
"And what we expect from the referees, is for them to be confident to maintain their authority on the pitch. To control and handle the players, and handle the game.
"We want referees to improve. We want to be in the best competition with the best players, the best managers and the best referees."
Asked whether he would stand by his comment that Mason was not good enough to officiate in the top flight, Nuno added: "The Premier League has the best system in referees, and when we go to a match we expect a referee not to be a protagonist of the situation.
"We want the referee to let the game flow and especially to control the players.
"We have to make players understand it is a tough job, but at the same time they have to be co-operative and help the referees, as long as the referees have the dialogue like they always do."