A rep for Justin Bieber has dismissed claims he spat in someone's water bottle and made snide remarks at a fellow gym user.

Radio presenter Collete Harrington says she was working out at the Ritz-Carlton hotel gym in North Carolina when Bieber, a trainer and a dancer entered.

She says the singer refused to sign an autograph before mocking her workout with his buddies.

Harrington then alleges that someone - either Bieber or one of his team - spat blue Gatorade into her water bottle, which she inadvertently drank.

A rep for the 'Believe' star told TMZ that the woman is "wrong" and that whilst he was in the gym, the comments between his friends were not directed at Harrington.

Watch Bieber perform acoustic below: