Canadian singer Benoit David has been dropped as the frontman of Yes ahead of the band's Australian tour after contracting a severe respiratory illness.

David had replaced band co-founder Jon Anderson in 2008, but the star was forced to put his career with the rock supergroup on hold last year as his condition worsened.

Now his time with the British band has officially come to an end - but David reveals he only discovered his exit was permanent after reading a recent magazine interview with founding bassist Chris Squire.

Eighteen separate musicians have come and gone since progressive-rock pioneers Yes formed in 1968. Confirming the news to fans, a heavy-hearted David said: "As you all know, the final three shows of last year's European tour were cancelled due to my ill health. 

"On my return to Canada, I was advised to cease touring, for the foreseeable future, in order to avoid further damage to my voice. Following this extremely disappointing diagnosis, I had no alternative but to inform my fellow band members that I was unable to confirm my availability for, at least, the forthcoming concerts in New Zealand, Australia and Japan...

"The band members were all very understanding and asked if I would mind being replaced for the April shows - I immediately agreed that this would be the best way forward and gave them my blessing...

"I subsequently learnt, from a band member's interview, that I had officially left Yes and that my departure was permanent," David said. 

"As this is the situation, everyone should know that I will be eternally grateful for the opportunity I was given... To the fans who have applauded my efforts and to those I have had the pleasure of meeting - many thanks, my best wishes and please continue with your support of one of the world's greatest bands."

Vocalist Jon Davison has since been recruited to take David's place and the group will play its first shows with its new frontman in April.

* Yes will play Bluesfest in Byron Bay on April 9 and sideshows in Sydney and Melbourne.

AAP