O'Reilly, 55, also filed a lawsuit. It claims the alleged victim of the harassment, Fox associate producer Andrea Mackris, 33, threatened him with the lawsuit in an attempt to extort hush money from the Fox News star.
The Smoking Gun first reported the charges and counter-charges and posted a copy of Makris' lawsuit on its Web site.
Mackris' lawsuit asserts that during a phone conversation this August, O'Reilly suggested she buy a vibrator and was clearly excited. Before hanging up, she said, O'Reilly told her: "I appreciate the fun phone call."
She contended he made a similar call Sept. 21, ending that one by saying: "Next time you'll come up to my hotel room and we'll make this happen."
In his countersuit against Mackris and her attorney, Benedict Morelli, O'Reilly said Morelli demanded $60 million in "hush money" to not file the lawsuit.
"As a public figure, I have received many threats," he said. "But enough is enough ... The threats stop now. I will not give in to extortion."
O'Reilly's lawyer, Ronald Green, said he believes there are tapes of conversations between the two and asked a court to compel Mackris to produce them so they could be played publicly.
"I know that he does not fear what is on the tapes," Green said.
Morelli would not comment on whether any taped phone conversations exist.
Besides the attempt for money, O'Reilly charged that his accuser and her lawyer were trying to embarrass him and Fox News Channel three weeks before the election. Morelli, he said, is a contributor to the Democratic Party; "The O'Reilly Factor" is a particular favorite among Republican viewers.
Morelli said his political contributions had nothing to do with the case.
"When he sued me today, I understood what kind of bully he is," the lawyer said. Mackris sat next to Morelli at a news conference Wednesday, but did not speak and would not answer questions.
A former White House intern in the first Bush administration, Mackris began working for O'Reilly in April 2000. Her complaint said that the first time she noticed odd behavior by O'Reilly came in 2002, when the Fox host allegedly urged her to use a vibrator after her engagement broke off.
Mackris' complaint said she told O'Reilly she was not interested in phone sex and felt "trapped" after his first inappropriate phone call.
Mackris never complained to anyone at Fox about untoward behavior by O'Reilly, Green said. When she returned to Fox earlier this year, O'Reilly agreed to match her salary at CNN, the network said.
Fox produced an e-mail Mackris sent to a friend last month, saying things are "wonderful, amazing, fun, creative, invigorating, secure, well-managed, challenging, interesting fun and surrounded by really good, fun people. I'm home and I'll never leave again."
Mackris said in her lawsuit that she told O'Reilly she would return to Fox only if he stopped the inappropriate behavior.
She said O'Reilly told her: "If any woman ever breathed a word I'll make her pay so dearly that she'll wish she'd never been/ born. I'll rake her through the mud, bring up things in her life and make her so miserable that she'll be destroyed."
On his show Wednesday, O'Reilly called the case "the single most evil thing I have ever experienced, and I've seen a lot. But these people picked the wrong guy."
One of the defendants named in the lawsuit against O'Reilly is Westwood One, which distributes his radio program. Westwood One is managed by Infinity Broadcasting. Infinity Broadcasting and CBS are both owned by Viacom.