(contactmusic.com) - Ne-Yo is set to sue fellow singer Beyonce Knowles over royalties to her 2006 hit single Irreplaceable, according to U.S. reports. The So Sick hitmaker - real name Shaffer Smith - is allegedly planning on launching a lawsuit against Knowles claiming she reneged on a promise to collaborate on his next album. Smith helped put together the song - from her B'Day LP - organising the vocal arrangement and the melody for free as part of an understanding that the former Destiny's Child star would return the favour on the follow up to his 2007 record Because Of You, according to MediaTakeOut.com. But the U.S. website is now reporting Knowles has refused to record a duet with the singer and Smith is now considering legal action in a bid to re-coup some of the money from their previous collaboration. A source tells the site, "(Ne-Yo) was never paid for writing the song Irreplaceable. There was just an understanding that he'd help out on (Beyonce's album) and when it was his time to make his album, Beyonce would return the favour. "It doesn't look like Beyonce's going to be working on the album. Ne-Yo could have sold that song for hundreds of thousands of dollars. I know that he's consulted a lawyer over what to do about things. "I'm not sure whether (Ne-Yo) will actually go through with a lawsuit. But I know he's furious about it. If she doesn't work on his album, I hope he does sue." Smith is currently suing R. Kelly's promoter, Rowe Entertainment, for breach of contract after Ne-Yo was dropped as the support act from the 40-year-old's Double Up tour in November (07).