Manchester City are unhappy that the FA are taking action against Roberto Mancini while Sir Alex Ferguson has not been charged for his rant at officials in the Boxing Day games.
But Ferguson, who launched into a tirade against referee Mike Dean, fourth official Neil Swarbrick and assistant referee Jake Collin before the second half of Manchester United's 4-3 win over Newcastle, has escaped punishment.
City believe that Friend should have awarded them a free-kick, for Craig Gardner's challenge on Pablo Zabaleta, in the build-up to Adam Johnson's winner and argue that Mancini, who often uses humour in press conferences, was only joking when he implied the referee was overweight.
The FA could not charge Ferguson because Dean did not send him to the stands or mention it in his referee's report, which was submitted the following day.
The Scot's anger stemmed from Newcastle's second goal, a Jonny Evans own goal, which he felt should have been deemed offside.
The United manager, meanwhile, hit back with a verbal assault against Pardew in his Friday press conference.
The FA have also written to QPR manager Harry Redknapp, who said a linesman "should have gone to Specsavers" after his 2-1 defeat to West Bromwich Albion.
Both men have until 5pm on Wednesday to respond to the FA.