Derby County have made an official complaint to the Football League after bitter rivals Nottingham Forest failed to pay a £90,000 bill.

The League are investigating after receiving a complaint from Derby over a late payment related to money from ticket sales for last month's game at the iPro Stadium. Forest have failed to pay their East Midlands neighbours on time for the second successive year and Derby have notified the League for assistance.

Championship clubs have to reconcile the monies from seats sold to their supporters at away grounds within a week after the game, but Forest have missed the deadline.