A popular Columbia professor was charged Thursday with incest – accused of a sick sex relationship with a female relative, prosecutors said.

David Epstein, 46, was charged Thursday with one count of third-degree incest. Police told the Spectator that the relationship appeared consensual.

Political science Prof. David Epstein, 46, had sex with the young woman over a three-year period ending last year, according to court papers.

He was arraigned before a Manhattan judge on a single felony incest count.

“We ask that everyone remember that he is innocent until proven otherwise and that these allegations are nothing more than allegations,” said Epstein’s defense lawyer Matthew Galluzzo.

University spokesman Robert Hornsby said that Epstein “is now on administrative leave and will not be teaching students.”

Epstein, who specializes in American politics and voting rights, has taught at Harvard and Stanford and often is quoted by news organizations. He also has blogged on The Huffington Post.

Sources said the victim was over 18 when the relationship began in 2006 and that the two often exchanged twisted text messages.

Epstein faces up to four years behind bars if convicted.

He was released on his own recognizance.

Epstein also blogged for this website, on topics ranging from torture to Sarah Palin.