The Football Association has written to Harry Redknapp and Roberto Mancini over their criticism of referees, reports BBC Sport. QPR boss Redknapp spoke of "scandalous" decisions in the 2-1 Premier League defeat by West Bromwich Albion on Boxing Day.
Manchester City boss Mancini accused officials of missing a foul on Pablo Zabaleta in the build-up to Adam Johnson's winner in the 1-0 defeat at Sunderland.
Both could be charged with improper conduct.
The FA sent letters to both managers, requesting their observations on their post-match comments.
