The Football Association are looking into comments made by Manchester United boss Sir Alex Ferguson and his Blackburn counterpart Sam Allardyce about the refereeing in their team's matches at the weekend. Ferguson questioned referee Alan Wiley's fitness after Manchester United's 2-2 draw with Sunderland, while Allardyce criticised Peter Walton for not giving a penalty for Thomas Vermaelen's apparent trip on David Dunn in Blackburn's 6-2 defeat at Arsenal.
A spokesman for the FA said: "We are reviewing the comments in their full context."
Professionals union Prospect, who represent referees, have defended Wiley, describing Ferguson's comments as "totally unwarranted".
Alan Leighton, the national secretary of Prospect, told Sky Sports News: "The referees never want to be the centre of attention in games and it is disappointing that yet again they are put in that position.
"My main concern is about the unfounded and totally unwarranted remarks about Alan Wiley's fitness.
"Not only does it dig at the heart of Alan's professionalism where he is one of our top and longest-serving referees, but it also has an impact on all the others.
"I understand that Sir Alex made comments about other referees and said about European referees being fit as butchers' dogs, comparing them with some referees from the UK who aren't fit.
"All of the referees, all of the officials and all of the assistant referees pass stringent fitness tests at the start of the season.
"Prozone statistics are used to monitor their performance in every game. If Alan Wiley or any other referee were not fit they would not be refereeing."
Rovers boss Allardyce could be in trouble after he questioned whether Walton was good enough to referee in the top flight after turning down a Rovers penalty claim at the Emirates Stadium.