Newt Gingrich has denied allegations by his ex-wife Marianne Gingrich that he sought an open marriage.

Marianne made her claim during an interview broadcast Thursday in most markets after the conclusion of CNN's Southern Republican Debate in Charleston, South Carolina.

In speaking to ABC Nightline's Brian Ross, Marianne said Newt asked her to “share” him with his mistress Callista, whom he later married after divorcing Marianne.

“If he's running for president he has answers to give,” Marianne told Ross.

“I found out during our conversations that it was occurring in my bedroom, in our apartment in Washington. And he always called me at night. He always ended with 'I love you,' while she was there listening.”

During his tenure as speaker of the House, Newt criticized President Bill Clinton for having an affair with Monica Lewinsky. He also supports a constitutional amendment that would define marriage as a heterosexual union.

During the GOP debate, he denied Marianne's claims and went on to scold moderator John King for asking the question.

“Let me be quite clear. This story is false. Every personal friend I have who knew us in that period says the story was false,” Newt said angrily.

“I think the destructive, vicious, negative nature of much of the news media makes it harder to govern this country, harder to attract descent people to run for public office. And I am appalled that you would begin a presidential debate on a topic like that.”

“To take an ex-wife and make it two days before the primary a significant question in a presidential campaign is as close to despicable as anything I can imagine,” he added as the audience cheered.

The claims, however, have not slowed down Newt's momentum in conservative South Carolina, which holds its presidential primary on Saturday. Polls indicate Newt could win the state.