Justin Bieber says being snubbed at the Grammy Awards is a "big bummer".

The 18-year-old pop star is unhappy his album 'Believe' didn't earn him a single nomination and was shocked he didn't make the cut despite the record's commercial success.

Speaking on 'The Ellen DeGeneres Show', he sighed: "I was looking forward to [a possible Grammy nomination], but I know it will happen one day. I'm so young, I'm only 18. I'm just blessed to be able to do what I love every day. And the AMAs was a lot of fun for me so ... Hopefully, one day."

Justin - who lost out for Best New Artist and Best Pop Vocal Album two years ago - was also quizzed about his casual attire while meeting the Canadian Prime Minister last month, after he was criticised for greeting Stephen Harper's hand while wearing overalls and a back-to-front baseball cap.

The teen idol insisted he would never have worn such a laid-back look had he been at a formal government event, and claims the meeting was so last minute he didn't have time to change.

He said: "I was at my concert. I was doing, like, a meet and greet, meeting all my fans and stuff, and [Stephen] came to the venue where I was performing. I know it wasn't fair but that was really my event. I really promise, if I would of went to his environment, I would have been all done up."