Referees' chief Howard Webb admitted Nathan Ake's goal against Fulham should have been disallowed for offside in their 5-1 victory on Saturday.
Ake's header regained City's lead to put them 2-1 up on the stroke of half-time but Fulham complained about Manuel Akanji being stood in an offside position and appeared to affect Bernd Leno in the goal.
After a VAR review of the incident, the goal was given and City went on to win the match comfortably by four goals.
Following the game, Erling Haaland - who scored a hat-trick - said he thought the goal should have been ruled out for offside, while Fulham boss Marco Silva also continued his complaints and said it should have been 'impossible' to allow the goal to stand.