The former Bill actor, who is currently appearing in Dancing On Ice, is said to believe that portraying the Nirvana frontman would be something "totally different".
The Sun says that the part is in Kurt and Sid, a play about a fictitious meeting between Cobain and Sex Pistols star Sid Vicious hours before Cobain's suicide.
"Playing Kurt Cobain would be far removed from the glitz and glamour of doing Dancing On Ice," a source said. "Gary wants a new challenge and this would certainly be that."
Shaun Evans has previously appeared as Cobain in the play.