Anderlecht have reportedly filed a complaint to FIFA following Harry Toffolo's failed move.
The Nottingham Forest left-back looked set to join the Belgian side on loan until the end of the season before the January transfer window closed. However, a deal collapsed.
Anderlecht manager Brian Riemer said: "At 11pm, there was still an agreement, but due to, in my opinion, extremely unprofessional behaviour from Nottingham, Harry Toffolo was recalled. I was surprised it didn’t go through. In football, sometimes a deal is apparently not enough."