Raymond van Barneveld will no longer play at the Lakeside World Darts Championship after joining the rival Professional Darts Corporation.
Barneveld will play in the PDC Premier League this year
The Dutchman has quit the British Darts Organisation to play alongside the likes of Phil Taylor at the PDC World Championship in Purfleet, Essex.
Barneveld, 38, is a four-time champion at Lakeside and will now compete in the Holsten Premier League.
Only last month he denied rumours he was about to join the PDC.
He said: "The time was right for me to make the biggest move of my career.
"As a professional darts player, you want to play every week against the best players in the world, including the best, Phil Taylor."
Barneveld lost this year's final at the Lakeside to fellow Dutchman Jelle Klaasen and will now pit his wits against Taylor and five other top PDC players at venues across the country.
Barneveld said: "I have known most of the players for a long time and it will be difficult going into competitions when I am not the favourite.
"But I hope I will be able to turn that around soon."
BDO spokesman Robert Holmes said the organisation was disappointed to have lost a player of Barneveld's profile, particularly after he had indicated he would be staying.
He said: "It is very sad he is moving on when, not that many weeks ago, he vowed to come back and try and win a fifth title.
"He wrote us a letter saying that he had won everything with the BDO and was looking for a new challenge and it had nothing to do with anything else.
"We have no choice but to wish him well but what the BDO offers the BBC is a genuine world title and players are starting on their road to play at Lakeside next year.
"Last year we had 12 players making their debuts and that's brilliant for the sport."
Barneveld's debut in the Premier League starts at Blackburn on Thursday.