Nuno Espirito Santo was wrong to single out Lee Mason for criticism but the standard of refereeing in the Premier League is falling, says former Professional Game Match Officials Board (PGMOL) chief Keith Hackett.

Wolves boss Nuno launched a scathing attack on Mason following his side's 2-1 defeat to Burnley at Turf Moor on Monday.

He said: "Honestly I don't like to say it, but I must say it because I will not feel right: the referee does not have the quality to whistle a game in the Premier League."

Hackett recalled his own dealings with some of the Premier League's most outspoken bosses and says while Nuno was wrong to specifically go after Mason, the Portuguese's concerns should be taken seriously.

"Of course, I've had to put up with that when I was the boss - it was [Alex] Ferguson, [Sam] Allardyce, [David] Moyes, [Arsene] Wenger and the like because these guys are passionate people and you have to take that into account," Hackett told Stats Perform News. 

"I think the reality is that some of our referees are less athletic in appearance than some of our European counterparts. I think in addition to that, referees have form. 

"Initially what he said was unfair because I think he personalised it. What he said obviously had some credibility because of his disappointment in decisions - which weren't specific to one decision, it was actually his overall management.

"So, it has to be taken seriously. I do think standards have fallen and I think for many reasons. 

"You get a quiet guy like Nuno who comes out and makes the biggest blast on a referee for the last two or three years and, yes he's wrong for personalising it, but I can understand his frustrations because I share some of his frustrations when I see the referees."

Hackett stressed the importance of the PGMOL communicating with managers and says referees do take it personally if they make a bad decision.

"I think we have to look at the facts and answer the facts to Nuno, that's Mike Riley's job in saying 'here is the information, what area of the performance are you criticising'?" Hackett added.

"I think the perception is they [referees] couldn't care less, I've dealt with referees for a long time, if you see the face of a referee after he's found out he's made a major error, it's really telling. 

"We're dealing with human beings, Lee Mason is towards the older end of the group in terms of age. Off the field of play you couldn't wish to meet nicer guy, great sense of humour.

"Sadly, and I have managed him, he doesn't take that onto the field of play and sometimes he's a rabbit in the headlights, and sometimes he's running where he shouldn't run and his game reading, even though he's an experienced referee, is lacking. 

"We can talk about technology, talk about competency levels but we've also got to say 'look these guys are human beings' and if you think Lee Mason listening into the comments made by Nuno Santos is going to be happy, he's not, because he's been personally attacked."