The Red Devils manager, furious at Andre Marriner's decisions during Tuesday's 2-1 defeat to Sunderland, suggested that his side were "having to play the officials"
The Red Devils were beaten 2-1 by Sunderland in the first leg of their Capital One Cup semi-final on Tuesday and the aggrieved Scot felt that both Black Cats goals came from wrong decisions, one a free kick and one a penalty.
Moyes told the press after the game of Andre Marriner's performance: "I thought the referee was going to blow in our direction for the first goal. I couldn't believe he gave a free kick. It was a terrible decision.
"We are all just laughing at them at the minute. We get a player booked for doing the same. It looks as though we are having to play them [officials] as well as the opposition at the moment."
The FA has confirmed they are looking into those comments, and is also looking into the throwing of flares during Tuesday's game, which appeared to come from United supporters.
United player-coach Ryan Giggs agreed with Moyes's frustrations regarding refereeing, describing the number of decisions going against his side as "laughable".