Ferguson was fuming with Wiley's handling of last week's 2-2 draw between Manchester United and Sunderland at Old Trafford and immediately after the game launched a stinging attack on the Staffordshire official.

Although it was widely interpreted as a diversionary tactic aimed at deflecting attention away from a poor performance by his team, Ferguson made a series of personal statements about Wiley's fitness, including a belief that he took longer than necessary to book players because he "needed a rest".

The views outraged Wiley's colleagues, amid claims that the referee himself felt like quitting the game because he was so upset at Ferguson.

The United manager had been pictured laughing and joking with him immediately after United's controversial late winner in the sixth minute of added time against Manchester City a fortnight earlier, when Wiley had been fourth official.

Ferguson has been asked to submit his own thoughts to the FA by next Friday (October 16) and could be facing a hefty fine, or a touchline ban.

However, before that, the Scot intends to ring Wiley to apologise, having concluded his attack was ill-judged.

"I apologise to Mr Wiley for any personal embarrassment that my remarks may have caused and to the FA for going public with my views," he said.

"In retrospect, I accept that this could be deemed as expressing those views in an inappropriate forum. "It was never my intention to bring the focus of intense media attention on Mr Wiley. I intend to contact him personally after I return from a trip overseas during this international break.

"I would wish it to be noted that I have always respected Mr Wiley's integrity and that I did not state or imply that Mr Wiley is a bad referee, that he was in any way biased, that decision-making generally during the game was poor, or that he missed any key incident during the game.

"My only intention in speaking publicly, was to highlight what I believe to be a serious and important issue in the game, namely that the fitness levels of referees must match the ever increasing demands of the modern game, which I hope will now be properly addressed through the appropriate formal channels."

Although analysts studied the match and concluded Wiley covered far more ground than the vast majority of the players, Ferguson does feel he has brought a relevant topic into the public domain, even if the manner was hardly in keeping with the FA's on-going Respect campaign.

Few would argue against a belief that the game at the highest level is now faster than ever, with referees under increasing pressure to improve their own fitness levels as a result.

The League Managers' Association and Professional Footballers' Association combined to produce their own blueprint for improving standards in refereeing earlier this year, which LMA chief executive Richard Bevan feels need to be heeded.

"In March 2009 the LMA and the PFA published the document Refereeing : A Professional Way Forward, which contains recommendations in respect of supporting referees and improving overall standards and is complimentary to the Respect Programme," he said.

"The aim of the document was to produce a set of serious proposals which would improve the selection, training, assessment and professionalism of referees at the top level of English football.

"The conclusions and recommendations of the review are compelling."