Justin Bieber's rapper pal Lil Za and hip-hop mogul Mack Maine have spoken out in defence of the troubled pop singer as his race row continues.

The Baby hitmaker has been engulfed in controversy since two video clips emerged this week (beg02Jun14) showing him using the N-word in a racist joke and singing about joining notorious hate group the Ku Klux Klan.

Bieber has apologised twice after the release of the two clips, which are several years old, saying, "I just hope that the next 14-year-old kid who doesn't understand the power of these words does not make the same mistakes I made..."

Now Maine, who is also president of Lil Wayne's record label Young Money, has spoken out to insist Bieber has never been disrespectful in his presence.

He tells Tmz.com, "Bieber does not have a slave mentality. He treats his people with respect... I remember telling a white man, Chinese man, Black man joke as a kid that was terrible and I told it to my friends because I thought they'd think it was funny."

Maine adds that Bieber has since "legitimately adopted the culture of the hip-hop, African American culture".

Bieber's close friend Lil Za has also come out in defence of the embattled star, posting a picture of the pair hugging on his Instagram.com page, and adding in a caption, "This guy right here changed my life and others in many ways. A true brother and friend, you're appreciated and loved by all of us and millions of fans."

Lil Za hit headlines earlier this year (14) when he was arrested on suspicion of drug possession following a police raid on Bieber's California home.