The singer, who started filming the BBC One show last month alongside Tom Jones, will.i.am and The Script's Danny O'Donoghue, told the Daily Star Sunday that it is important to offer constructive advice in the music industry.
She said: "I may be young but I'm not scared of being critical. I like how Simon Cowell says exactly what he thinks, whether people like it or not. I don't care if people don't like me and I'm prepared for that.
"Even if they are on my team, that doesn't mean I'm going to say it was good if it wasn't. I'm not a robot. I sing out of tune sometimes so I'm not scared to tell someone else if they have. I'm going to be honest. That's what the industry needs more of right now."
Speaking about her debut on the show, she added: "I'm not going to lie. I'm sh**ting myself, but in a good way. And I'm really happy that I'm the only girl on the panel."
Jessie J teamed up with her fellow Voice coaches to perform a cover of the Black Eyed Peas song 'I Gotta Feeling' while filming the auditions.
Cheryl Cole has been tipped to debut her new single on the show when it starts in the spring.
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Watch Jessie J in her video for 'Domino' below: