Janet Jackson’s music mogul boyfriend has lashed out at Justin Timberlake in his new book, branding the pop superstar "ordinary looking" and a "skinny white kid".

Producer Jermaine Dupri takes issue with Timberlake in the grandly-titled The Making Of A Mogul: Young, Rich & Dangerous, because he thinks the SexyBack singer could be much bigger if he worked on his image.

He says, "I'm giving people my perspective as a music person, who creates artists from scratch.

"I have a new artist that's coming out and he told me that he wanted to wear suits as his image... To me, that's not gonna do anything, that's not gonna set you aside from anything.

"I don't believe that the image that [Timberlake] gives me even makes me believe that he's as big star as he could be... I believe that his music is incredible but he doesn't have anything else to go along with the music."

Some have suggested that Dupri’s his attack on Timberlake is payback after the star’s public criticism of Janet following her infamous 'wardrobe malfunction' during their 2004 SuperBowl duet.

Dupri sidesteps the claims, saying, "I don't say anything about the SuperBowl in that whole statement."