The world's former fifth-ranked player, who won five events in his 21-year pro career, was found guilty of manipulating seven matches in 2008 and 2009 and received the heaviest fixing sanction ever imposed by the sport.
"The fixing occurred at several top events in the sport, over a sustained period, and is damaging to its reputation," independent tribunal chairman Adam Lewis said. "While Mr. Lee may not have been the prime mover or instigator, the gambling was undertaken through three separate groups, and it is unlikely that Mr. Lee was simultaneously led astray by all three."
Lee said he will appeal.
"I'm absolutely devastated. I've done nothing wrong," the 38-year-old Englishman said. "I'm totally innocent from this."
It's the biggest case of match-fixing in snooker since Australia's Quinten Hann was suspended for eight years in 2006.
Lee was found guilty of fixing matches at the 2008 Malta Cup, the 2008 U.K. Championship, the 2009 China Open and the 2009 world championship.
Lewis said a life-time ban was not "proportionate, or as necessary in order to deter" other match-fixers.
But the governing body believes Lee's career is effectively over. His ban runs until 2024.
"In effect it is a life ban because I think it is highly unlikely that Stephen Lee will be able to come back to the sport at this level," World Professional Billiards and Snooker Association disciplinary head Nigel Mawer said. "We don't take great pleasure out of that. This is a case of a fantastic snooker player who has thrown it all away through making the wrong decisions."
The tribunal found that Lee was in a "financially perilous state" and was taken advantage of while in a vulnerable position.
The WPBSA established that Lee did not deliberately lose matches he could have won, but cheated in matches he believed he would either lose or win comfortably enough to drop the first frame.
"Lee did not strike me as a cynical cheat, but rather as a weak man who under financial pressure, succumbed to the temptation to take improper steps that he may well have justified to himself as not really wrong, because the ultimate result of the match, win or lose, was the same," Lewis, the attorney who headed the tribunal, said in his findings.
Even if the end result was not fixed, Lewis concluded that participants and spectators are entitled to see a clean contest.
"For each bet won on the back of spot-fixing, there is a counterparty who has been wrongly deprived of money," Lewis said. "With the growth of betting exchanges, those counterparties will often not be bookmakers."
The tribunal was unable to determine how much Lee profited from his fixing.