The 35-year-old singer recently performed his new single Hollywood on the British talent show and said he was 'shocked' that there were rumours circling on the Internet that accused him of miming.
He said to BBC Radio One: 'Whoever you are writing on these blogs if you think that I'm miming you're an idiot.'
He added: 'Did they not listen to me I was flat and out of breath.'
Buble admitted that he was ill before the performance and had to change how he sung.
He said: 'I had to go down a key because I was sick and couldn't hit the notes. If I was going to lip synch wouldn't I just do it to my recording.'
His comments come after Cheryl Cole, who also performed the same night that Buble did, was accused of miming parts of her performance.