Justin Bieber N-Word Hoax -- DON'T BLAME ME ... Says Bieb-alike Singer

The R&B singer who actually said the N-word in a song many people confused for a Justin Bieber track tells TMZ ... he's NOT to blame for the hoax ... but he thinks he knows who did it.

As we previously reported, several media outlets fell for a lame YouTube hoax this week ... when someone created a bogus "official" Justin Bieber account and posted a song in which the singer dropped the N-Word.

Turns out the song was actually a track by a singer named Khalil Underwood ... an aspiring R&B singer, who happens to be black (which explains the casual n-bomb in the song).

After the hoax, several people pointed the finger at Underwood ... claiming he operated the scheme in a shameless attempt to gain publicity.

But Underwood tells TMZ ... that simply ain't the case -- he's just an innocent bystander who was roped in to the hoax because he happens to sound like Bieber.

In fact, Underwood says he thinks the real perpatrators are Beliebers who truly believed the song was a Justin original and tried to "leak" it on YouTube.

Underwood says the funny part .. Beliebers were saying they liked the song when they thought it was a JB original, and when they learned the truth, they changed their minds.