Manchester United manager Sir Alex Ferguson and his assistant Carlos Queiroz have been cleared of a charge of improper conduct by the Football Association. The charge related to comments made following United's FA Cup defeat to Portsmouth on March 8. Ferguson's charge concerned comments about referee Martin Atkinson and Professional Game Match Officials (PGMO) general manager Keith Hackett. Queiroz's charge related to comments about Atkinson. Speaking after Sulley Muntari's penalty gave Pompey a shock victory at Old Trafford, Ferguson felt his side had earlier had a blatant spot-kick denied when Cristiano Ronaldo was blocked by Sylvain Distin. 'It's absolutely ridiculous,' Ferguson said. 'I cannot explain it. Managers get sacked because of things like that and he's going to referee a game next week.' He added: 'He (Hackett) is not doing his job properly and he needs to be assessed. 'I'm assessed as a manager, players are assessed, referees should be assessed properly by the right people. That performance today should not be accepted by our game.'