Singer Russell Watson has pulled out of BBC One talent show Just the Two of Us, three months after having a tumour removed from his brain.
Russell Watson had a five hour operation to remove a brain tumour
The 39-year-old has been warned by his doctor not to take part in the series, which begins on 2 January.
A spokesman for Watson said he is "extremely disappointed".
Producers have decided not to replace Watson at such short notice. His partner, Loui Batley, will not appear in the competition either.
Hollyoaks star Batley said: "I was really looking forward to working with Russell so I am a bit gutted, but hope he gets well soon and I'll be cheering the other competitors on from the comfort of my sofa."
The classical singer had been recording an album in Los Angeles when the tumour was diagnosed. It forced him to postpone his UK tour, which had been scheduled to start last month.
Last year, Watson won the first series after stepping in at the last minute to replace Rick Astley, who was the original partner of actress Sian Reeves.
Russell Watson and Sian Reeves won the first series
Executive producer Sumi Connock said: "Obviously we're deeply disappointed that our champion can't return to defend his crown but we always knew that it was a possibility due to his health."
Ex-Blue Peter presenter Janet Ellis, cricketer Mark Butcher and actress Hannah Waterman are among those who will be taking part.
The programme - presented by husband-and-wife team Vernon Kay and Tess Daly - will run for six nights.
Each duo will be judged by a panel of industry experts before viewers vote for their favourites.