Peter Ebdon had to remove an advertising logo from his shirt before facing Ronnie O'Sullivan at the Crucible due to concerns it was illegal.
The Cancer Act of 1939 prohibits the advertising of "an offer to treat any person for cancer, or to prescribe any remedy therefor, or to give any advice in connection with the treatment thereof", and Ebdon's promotion of an alternative therapy was the subject of complaints following the first session against O'Sullivan.
World Snooker received several messages questioning whether Ebdon should be allowed to wear the Gerson Therapy logo.
A World Snooker spokesman said: "We were made aware the logo could breach rules relating to pharmaceuticals and therapy and he was told to remove the logo."
The 41-year-old Ebdon was unhappy with that step.
He said in his post-match press conference, after losing to O'Sullivan: "I wore a logo yesterday which I was told today I wasn't allowed to wear, because it offered an alternative cancer therapy treatment.
"Obviously I've upset somebody somewhere but personally I think it's too important for people not to know."
Ebdon has taken up a vegan diet since the death of his father, Michael, from cancer last year.
He broke down in tears during his press conference as he remembered his father, and said he was proud to have won the China Open earlier this month and qualified for his 21st consecutive World Championship.
Ebdon, giving his personal views, said: "I really hope I can promote a vegan lifestyle and let people know what I've learnt about cancer and the fact it's not the end of the world, even if you're diagnosed with terminal cancer, because there are treatments out there, there are natural treatments out there which work, and which work in the huge majority of cases."
The Gerson Therapy method, which focuses on healing through a diet of organic, raw, vegetarian food, is said by Cancer Research UK to be unproven.
The Cancer Research website states: "Available scientific evidence does not support any claims that Gerson therapy can treat cancer. In fact, Gerson therapy can be very harmful to your health."
Ebdon believes his vegan diet can bolster his prospects of winning another world title.
He said: "I can really look forward to the rest of my career and working hard, and I know that if I keep doing the right things, I know that I can come back and be champion here again.
"It's going to be a lot of hard work but I really believe I can and will do it."
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