SYDNEY, Australia — The lead singer of the hugely popular children's group The Wiggles announced Thursday he will stop performing because of illness.

In a video-recorded statement, Greg Page said he had been diagnosed with a chronic condition called orthostatic intolerance.

"It's not a life-threatening condition by any means, but it is one that's going to be with me for the rest of my life," said Page, 34, who is known for bright yellow T-shirt. "It means that I'll no longer be able to sing and dance as I want to, and as a result I've decided to stop performing with The Wiggles."

Orthostatic intolerance is a little-understood disorder that causes dizziness, fatigue and nausea.

Page, who helped found The Wiggles in 1991, handed his yellow T-shirt over to his understudy, Sam Moran, who has been performing with the group for more than a decade as a backup singer and dancer.

"I'll miss being a part of The Wiggles very much, but this is the right decision because it will allow me to focus on managing my health," Page said.

Page has battled health troubles since undergoing a double hernia operation last December. He withdrew from the group's U.S. tour in June after suffering repeated fainting spells and bouts of lethargy.

His fellow band members said they were sad and disappointed by the news at a media conference in the western city of Perth, where they were set to launch an Australian tour.

"It's very surreal that Greg's not going to be with us, very sad," said Blue Wiggle Anthony Field. "I know Greg loved doing the shows, it's just that he can't physically do it anymore."

Field, Page and the group's Red Wiggle, Murray Cook, met while studying early childhood education at Sydney's Macquarie University. They enlisted their fourth member, Purple Wiggle Jeff Fatt, and The Wiggles were born.

The group was rated by Business Review Magazine as Australia's top-earning entertainer last year, ahead of actors Nicole Kidman and Russell Crowe. The four men in brightly colored T-shirts, accompanied by a cast of characters including Dorothy the Dinosaur and Wags the Dog, grossed $39 million last year.

The group has franchised its enormously popular recipe to several non-English speaking countries, including Taiwan.