UPDATE: Hailey has responded to Jon's accusation that she is lying.
"Look, the documents and the evidence speak for itself," she told Radar.
Jon declined to comment on the story before it was published, Radar reports.
PREVIOUSLY: Jon Gosselin allegedly threatened to report ex-wife Kate to Child Protective Services if she pay him off, Radaronline.com reports.
Jon's ex-girlfriend, Hailey Glassman, tells Radar that Jon tried to extort Kate when their daughter Mady hurt her arm. Jon planned to tell CPS that Kate had caused the injury by yanking on Mady's arm.
"We were in bed and Jon called Kate on speaker phone," Hailey said. "He wrote down what he wanted to say to her and then he read from his notes. He told her, 'You either give me money, or I'm going to call CPS.'"
Hailey provided Radar with handwritten notes, allegedly from Jon, that support her story. The notes (see part of one below, click here for the rest) say things like "Need 50k or 100k now. 24/48 hours go to DA" and "Jon giving Kate ultimatums. He privately extorts Kate. If you don't do what I want, I'll do this..."
"He always referred to himself in the third person," Hailey said. "I found it so strange. It was almost like he thought he was still on camera."
Jon took to Twitter Wednesday to deny Hailey's claims.
"Radaronline has been duped again by Hailey Glassman, who is apparently without a job and desperate for money," he wrote. "This article contains so many lies, they are too numerous to count. It is completely false and without any merit."