Demi Lovato told James Corden he was the "best damn diva I've ever seen" on 'The Late Late Show'.

Demi Lovato

Demi Lovato

The pair had a sing-off on his CBS series on Wednesday night (05.04.17) as the 38-year-old host was out to prove that modern day divas aren't as good as the old ones.

However, after they duetted on Gloria Gaynor's 'I Will Survive' the 'Confident' singer declared James the biggest diva, and he settled on the fact Demi's renditions of Katy Perry's 'Roar' and Adele's 'Rolling in the Deep' confirmed the divas of this generation have plenty of sass.

Arguing his point, the funnyman said: "They didn't have Instagram -- they just had sass, voice, songs."

As the brunette beauty came on stage, she said: "I heard you've been telling people that divas back then are better than divas today."

However, at this point the British funnyman wasn't convinced and rolled off a list of the biggest divas of all time.

He said: "Well, yes, they are -Tina Turner, Aretha Franklin, Whitney Houston, Cher ... it's a fact. Divas back then were just fiercer than divas are today. It's as simple as that."

Demi then asked him to battle her, saying: "Why don't we just settle this tonight?"

The 24-year-old pop star then sung Adele's monster hit with the help of a cappella group Level. Her performance was met with loud applause from the studio audience.

However, when James launched into Tina Turner's 'River Deep, Mountain High', it was a different story.

Demi laughed: "Wow, that was terrible. Just really awful. Bad."

Corden told her to "watch" what she was saying and belted out Aretha Franklin's 'Respect'.

Before singing, he said: "You better watch your mouth.

"You know what you need, little lady? You need a little respect."

He then pulled up Demi for not performing her own songs after she did Katy Perry, but she came back with her song 'Heart Attack'.

After the performance, she jokingly concluded: "Can you pick my mic up ... bitch!"

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