Richard B. Jefferson said the 24-year-old singer hasn't expressed "any plans to voluntarily reveal additional incriminating evidence, which he possesses, to the general public that undoubtedly proves the extent of their involvement because of its explicit nature."
However, in an e-mail to The Associated Press Monday, Jefferson said Clark would "fully cooperate with any governmental agency that launches an investigation stemming from his claims."
Clark alleged last week that Abdul, a judge on the Fox talent competition, had an affair with him while he was competing in 2003 and also coached him on how to do better in the competition.
Jed Wallace, Clark's spokesman, refused to comment Tuesday on what type of "evidence" Clark might possess. Abdul's spokesman, Shawn Sachs, didn't immediately return calls seeking comment.
Last week, ABC's "Primetime Live" aired an expose of the scandal, which the "Saturday Night Live" cast lampooned on Saturday's show. At the end of the sketch, Abdul made her own "Idol"-style critiques of her imitator, saying to Amy Poehler: "You need to perfect the clap a little more and be a lot more sexier so contestants will be willing to sleep with you."
Abdul has called Clark's allegations "lies" and an attempt at character assassination. She issued a statement Friday expressing "my deepest appreciation" for fans who have expressed their support for her.
"Neither Ms. Abdul's vague statement nor her satire regarding this incident refutes her inappropriate relationship with Mr. Clark or discredits the veracity of his claims," Jefferson said in the e-mail.
The Fox network said Clark hadn't responded to requests for help investigating his charges. Clark said he had no interest in helping the show that booted him off.