Disgraced author Belle Gibson was secretly paid $75,000 for appearing on Channel Nine's flagship current affairs show, 60 Minutes, after her global cancer hoax and charity fraud were first exposed.

Ms Gibson has refused to disclose whether she was paid for participating in the explosive interview with host Tara Brown in June last year.

And the Nine Network has repeatedly said payments to interviewees are confidential, refusing to confirm or deny ongoing speculation. It was rumoured last year that Ms Gibson was paid as much as $45,000 to appear.

But documents obtained by Fairfax Media now reveal the broadcaster paid her much more for the exclusive interview. Invoices and remittance advice show Nine made two separate payments each of $37,500 to Ms Gibson's lawyers in July 2015 under the reference, '60 Minutes – Belle Gibson interview'.