The FA have charged Sir Alex Ferguson with improper conduct for his attack on referee Martin Atkinson after Tuesday's match with Chelsea.Although the Manchester United manager's comments on Sky Sports were critical of the official, it is the ones to his club's own in-house station MUTV where the FA believe he may have crossed the line by raising a question about Atkinson's integrity.The charge raises the prospect of Ferguson ending up getting a touchline ban thanks to evidence provided by his own club.Although the United boss might have kept his counsel on Wednesday and reflected on the changing fortunes of a game that should have left him playing with just 10 men at Wigan three days earlier, Ferguson opted to let fly with both barrels following a loss to Frank Lampard's controversial penalty.Ferguson labelled that decision, for Chris Smalling's foul on Yuri Zhirkov "soft" but it was the failure to send David Luiz off for a clear trip on Wayne Rooney after the Brazilian had already been booked that really annoyed the Scot."You want a fair referee, or a strong referee anyway - and we didn't get that," he said. "I must say, when I saw who the referee was I feared it. I feared the worst."Given the United boss already has the remaining two matches of a four-game touchline ban hanging over him following scathing comments about Alan Wiley's fitness last season, a further spell in the stands appears inevitable if misconduct is proved.It will not come into effect before Sunday's trip to Liverpool though as a "non-standard" case such as a manager's media comments is not heard with the rapidity of a normal case under the FA's fast-track disciplinary system, which means it is likely to be next week before any ban could be imposed.Source: Eurosport