The Manchester United manager Sir Alex Ferguson and his assistant, Carlos Queiroz, have been charged with improper conduct by the Football Association. The charges relate to comments made by the two men following United's FA Cup exit at the hands of Portsmouth last month.

A furious Ferguson criticised referee Martin Atkinson and the Premier League head of referees Keith Hackett after the 1-0 defeat at Old Trafford, in which United saw their claim for a penalty after an apparent foul on Cristiano Ronaldo turned down, before Atkinson awarded Portsmouth the decisive penalty and sent off United goalkeeper Tomasz Kuszczak after he had brought down Milan Baros.

"Managers get sacked because of things like that and he's going to referee a game next week," said Ferguson after the sixth-round tie on March 8. "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 should not be accepted by our game."

Ferguson and Queiroz have until April 17 to respond to the disciplinary charges, which come after one of Ferguson's former proteges, Roy Keane, last week made a thinly veiled jibe at his ex-manager, saying: "We have got to be careful who we listen to, there are a lot of hypocrites in football ... how can their players then show officials respect if their boss does not?"

Ferguson has been vocal in his support of a campaign to increase the respect shown to referees after poor behaviour on the pitch by high-profile players such as Ashley Cole and Javier Mascherano, and a survey by the League Managers' Association today found that many Premier League managers support the FA's "Respect" campaign. The LMA said it wanted to "perform an integral role" in setting the respect policybut warned that managers are frustrated by the inconsistency in the interpretation of offside rules.