The 37-year-old already sits on the panel in the States alongside Adam Levine, Christina Aguilera, and Blake Shelton.
Cee Lo had been offered a judge's spot on the show, in which the panel have their backs to the stage so the hopefuls can be judged on their voices alone.
But a scheduling clash means he has to stay in the States.
A source told British newspaper The Sun: 'He'd have been a great signing but he has to commit to the US show.'
Rocker Lenny Kravitz and singer Jessie J are said to be in the running for a slot on the series.