It’s a sing-off!

James Corden had some not terribly nice things to say about Adam Lambert continuing his gig as Queen’s singer -- but Lambert was more than prepared to defend himself.

“I’m not saying that I’d be a better frontman than him,” Corden said on Thursday’s “Late Late Show” while discussing Queen’s upcoming summer tour. “But I’m just saying that I would be a better frontman than him.”

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That boasting prompted Lambert to appear and challenge him.

But Lambert had a trick up his sleeve -- his Queen bandmates Brian May and Roger Taylor, who rolled out on stage to perform “We Will Rock You.” Corden shot back with “Don’t Stop Me Now,” getting in Lambert’s face and flipping the bird, which wasn’t very sportsmanlike.

They faced off further with “Crazy Little Thing Called Love” and “Another One Bites the Dust” before a clearly bested Corden conceded defeat to Lambert before ending on a duet of “Somebody to Love.”