Nielsen, 31, who is currently on loan to Stromsgodset in Norway, said in an interview with TV2 sports show LPS that the reason was because he amassed heavy gambling debts.

"This was during a period when I had just been involved in a playing scandal and had gambled a lot of money away, so when I got the chance to get some money back again, I took it," he admitted.

AaB lost the cup final to FC Copenhagen that year.

The Danish Football Association has asked the disciplinary committee to investigate the admission, which it described as "discrediting to the game of football."

The DBU added there were three observers at the May 2004 game and none of them had any idea that Nielsen was playing in an unsportsmanlike way.