Not a bit of it!
Definition 1 of 1
Pro Tip 1/3Strong Denial
Use it to clearly reject an assumption or statement someone else makes. 
You thought I was involved in the error? Not a bit of it!
Pro Tip 2/3Emphasis
Adds emphasis to your denial, making your 'no' stronger and more definitive. 
Was that my voice on the recording? Not a bit of it!
Pro Tip 3/3Informal Tone
It's informal and often used in spoken, casual contexts among friends or peers. 
Am I bored at the party? Not a bit of it!