The Red Devils have responded to criticism from LMA chief Richard Bevan and say the decision to replace the Scot was not taken until late on Monday night
Moyes' exit was confirmed on Tuesday morning after being widely reported on Monday and the former Everton boss has since spoken of his pride at being asked to lead the Red Devils.
However, League Managers Association chief Richard Bevan has hit out at United, accusing the champions of acting unprofessionally.
The Red Devils have now responded to his comments, insisting they acted properly and that the decision to replace Moyes had not been made when newspaper reports emerged on Monday afternoon.
"We do not accept that it was handled in an unprofessional manner," a Manchester United spokesman told Press Association Sport.
"The decision was not taken until late Monday night and was communicated face-to-face first thing on Tuesday morning.
"When reports started emerging on internet news sites on Monday afternoon, no decision had been taken at that time."
Ryan Giggs has subsequently been appointed interim manager at Old Trafford and Goal understands the club's owners, the Glazer family, are due at Carrington on Friday to discuss who should succeed the Scot.