Judith Regan has secret tapes of phone calls and meetings that provide explosive evidence in her $20 million lawsuit against Rupert Murdoch's News Corporation, sources tell us.

After attempting to publish O.J. Simpson's memoir "If I Did It," Regan was fired by HarperCollins' CEO Jane Friedman.

The tapes "not only bolster her position against News Corp, but may prove damning to more than a few Fox executives," one source, who characterized the recordings as "juicy," told us.