Illness has forced Jock Hobbs to stand down from his roles as chairman of the New Zealand Rugby Union and Rugby New Zealand 2011 Ltd with immediate effect.
NZRU chief executive Steve Tew said on Friday that Hobbs now requires treatment on a form of leukaemia he was diagnosed with last year.
"Jock and his family have asked that we respect their privacy at this difficult time," Tew said. "Jock's wisdom and guidance, his counsel and his friendship will be sorely missed around the table," he said. "We'll keep in touch with him, but I've said to him today that I will not ring him again for the next six months, at least not to talk about rugby.
"If we were to paint the most positive scenario, and he undergoes treatment and gets the leukaemia back into remission, then depending on what he decides in the next few weeks, we may be able to leave some doors open for him to come back. Certainly that's the stated desire of the government, and we would be very supportive of that providing his health is right."
Mike Eagle has been elected NZRU acting chairman, while deputy chairman of RNZ 2011 Brian Roche will act as chairman for the organisers of next year's World Cup until their board meeting on May 24. Hobbs' future involvement at the NZRU will be discussed at greater length at the NZRU's next board meeting on May 27.
RNZ 2011 chief executive Martin Snedden praised Hobbs for his key role in helping New Zealand win the hosting rights to the tournament and in the ongoing preparations for next year's showpiece.
"Our thoughts go out to Jock and his family at this difficult time. His passion and energy has contributed tremendously to our efforts to stage a successful tournament," Snedden said.
Hobbs, who has been chairman of the NZRU since 2002, revealed he had a chronic form of leukaemia in September last year which he said was being monitored.