Italian referee Pierluigi Collina has retired after resigning from the Italian Association of Referees (AIA).
The 45-year-old had been accused by the Italian Football Federation (FIGC) of a conflict of interest after accepting a sponsorship deal.
Opel, who also sponsor AC Milan, were to pay Collina £545,000 per year and the FIGC told Collina he would only be able to referee second division games.
"After 28 years I've decided to hand in my resignation," said Collina.
"People must believe in a referee. In the end, we have all lost out."
"I have slept less these last few nights than on the eve of the World Cup final.
"For me it wouldn't have been a problem to referee in Serie B, but either they (the FIGC) have faith in us referees or they don't.
"If they don't, then we have to go. Without trust we cannot move forward."
Collina, who has been voted the world's best referee five times, took charge of the 2002 World Cup final between Brazil and Germany.
He was due to retire in the summer but the Italian football association extended the maximum age for referees to 46 to accommodate him for a further year.
Collina will replaced for the 2006 World Cup qualifier between Spain and Serbia and Montenegro on 7 September by England's Graham Poll.
MMIX
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Match of the Day - Post-match interviews