Erik ten Hag criticised the performance of referee Andre Marriner after Manchester United lost 1-0 to Brighton.
Alexis Mac Allister struck a 99th-minute penalty after Luke Shaw handled from a corner but Ten Hag and Shaw were adamant the Brighton forward Julio Enciso should not have received a free-kick which led to the pivotal corner.
Ten Hag also accused Marriner, who sent off Casemiro against Crystal Palace in the only other United match he has officiated this season, of failing to clamp down on Brighton's tactical fouling.