'Poker Face' singer Lady Gaga has hit back at a music producer who claims that he launched her career and was later ditched by her.

In court papers that were made public, Gaga's lawyer said the agreement at the heart of the suit was "unlawful".

Songwriter and music producer Rob Fusari filed the 20.3 million pounds lawsuit on March 17 in Manhattan against the Grammy Award-winning performer for denying him his 20 percent share.

According to the lawsuit, Gaga and Fusari's relationship turned romantic and then became a business partnership in May 2006, when they created a joint venture called Team Love Child to promote her career.

But Gaga's lawyer Charles Ortner wrote in his response that the arrangement was "structured in such a way as to mask its true purpose - to provide to the defendants unlawful compensation for their services as unlicensed employment agents".

Ortner wrote that Fusari and his company violated statutes, which prohibited them from "acting as employment agents without a licence and charging Lady Gaga an unlawful fee for their purported services".

But Fusari's lawyer Robert Meloni called the claim "ludicrous".

"Fusari is a partner in the Team Love LLC with Gaga and her father (through their company Mermaid)," the Daily Express quoted Meloni as writing in an email.

"Rob was no more of an 'agent' for her than she is a Roman Catholic nun," he added. (ANI)