Soulja Boy has revealed that he is the mastermind behind Willow Smith's 'Whip My Hair'.

The rapper has claimed that wrote the lyrics to the 10-year-old's top ten hit.

He posted the news on his Twitter: "YES ITS TRUE I WROTE "WHIP MY HAIR" FOR WILLOW SMITH. THATS WHY SHE SAYS HOP OUT THE BED TURN MY SWAG ON. WE GETTING $$$ 2011 NO GAMES (sic)"

Soulja Boy is rumoured to have trademarked the phrase "turn my swag on", Digital Spy reports.

Meanwhile, Willow Smith missed out on becoming the youngest chart-topper since Little Jimmy Osmond in 1972 after Black Eyed Peas beat her to number one back in December.

(by Holly Frith)