The Football League are seeking compensation from Wembley after a double-booking for the Champions League final and the play-off finals at the stadium on the same day in 2011.
The national stadium was chosen by Uefa last month to host the 2011 Champions League final - which from next season is to be played on a Saturday.
But in 2011, the date - 28 May - clashes with the first day of the Football League's play-off weekend, what would normally be the League Two play-off final.
The Football League are one of Wembley's most important customers - they have a 100-match contract with the stadium and a booking for the May bank holiday weekend stretching over 20 years.
It is understood League chiefs are demanding compensation if they have to move one of the play-off finals to another venue such as Cardiff's Millennium Stadium - neither Uefa nor the Metropolitan police will look kindly on another final taking place in London on the same day.
Talks between the League and Wembley officials are continuing but it looks certain the stadium will have to pay compensation for the breach of contract.