The Football Association have written to Chelsea manager Avram Grant to ask him to explain his remarks about referee Steve Bennett.
Grant called Bennett's integrity into question after Manchester United's 2-0 win at Wigan last Sunday earned a 10th Premier League title for Sir Alex Ferguson.
The Blues, level on points with United before kick-off, could only draw at home with Bolton on the final day of the season.
But Bennett came under fire for not awarding the Latics a penalty for handball and then opting not to send off Paul Scholes for a second bookable offence when he fouled Wilson Palacios.
At his UEFA Champions League media conference on Wednesday, Grant said: "I told you that I believed in the tradition of the fair English game. I will not say anything against it. But what happened is what I expected.
"In England there are very good referees, but there are some - a few that you can influence, like you saw.
"I think in our game against Manchester United at Old Trafford, the referee (Mike Dean) influenced the result for sure. We know that.
"I think the red card for Mikel John Obi in that game should not have been a red card, I think that Paul Scholes should have had a red card on Sunday and Wigan a penalty also.
"But it is finished. I congratulate Manchester United."
The Israeli, who has guided the west London club to the UEFA Champions League final against the Red Devils on 21 May, has until the 28th to reply.