The Daily Mail says United are adamant their allegations of racism by Chelsea groundsman Sam Bethell towards their defender Patrice Evra at Stamford Bridge 12 days ago should be fully investigated, providing a tense backdrop to Sunday's title climax.
With United and Chelsea locked on the same number of points ahead of the final day of the League season and due to meet in the Champions League Final in Moscow on May 21, the clubs will be in each other's faces for the coming fortnight.
United claim Bethell made a racist comment to Frenchman Evra after the two men traded blows in the wake of Chelsea's 2-1 Premier League victory over the champions on April 26. After a week or so of United lawyer Maurice Watkins interviewing staff and players, United have submitted their version of events and are prepared to stand before an FA inquiry if the issue goes that far.
It is understood Evra has re-iterated he did not hear anything racist from Bethell, but United have written evidence from at least one senior player and one member of their coaching staff that an offensive comment was made.
Bethell has denied saying anything racist and Chelsea will vigorously deny any such accusation in the belief they have evidence to prove their case. They may even allege that United changed their position over what happened four times during the day after the game.