The chatshow host, 46, said that he snubbed an offer to join the panel on the David Dimbleby-helmed topical debate series because he did not want to steal the limelight from politicians.
"I don't even care what I think, so why would anyone else!" he told DS.
"I think politicians are so rarely funny, so if they manage to make a joke let them have their moment. It's so unfair to say, 'well you thought that was funny, but here's Jo Brand or another comedian with an even funnier comment'. Let's not muddy the waters."
Celebrities including Will Young, Fern Britton and Jarvis Cocker have appeared on the BBC One series in the past.