The author of best-selling novel “The Exorcist” says he plans to sue alma mater Georgetown University in a Vatican court after the Catholic school invited Health and Human Services Secretary Kathleen Sebelius to speak on campus.

The author, William Peter Blatty, says the Jesuit-founded university in Washington has for the past two decades invited speakers who support abortion rights and has refused to comply with orders by the late Pope John Paul II for church-affiliated colleges and universities.

The “last straw” was the university allowing students to invite Sebelius to speak May 18, considering she was instrumental in helping President Obama draft health care reform that includes a mandate for some religious institutions to offer insurance to cover employees’ birth-control costs, said Blatty, who attended Georgetown on a scholarship and graduated in 1950.

“I owe much to the Jesuit fathers and to Georgetown University,” Blatty says on his The Father of King Society website. “What I owe Georgetown, however, is nothing as compared to what Georgetown owes to its founders and the Christ of faith.”

On the website, the 85-year-old Blatty also encourages others to show their disappointment by cutting off donations to Georgetown for a year.

His 1971 book about a young Jesuit priest who tries to help a girl possessed by a demon became an blockbuster movie and won Blatty an Academy Award for screen writing.

The suit will be filed with the Vatican and the Archdiocese of Washington, asking the church to remove Georgetown’s right to call itself Catholic, according to the Cardinal Newman Society, which Blatty has asked for guidance.

The Archdiocese of Washington and several religious groups also disagreed with inviting Sebelius, who received mostly cheers and some boos during her speech.

Georgetown officials have said the school has a long history of hosting a wide range of speakers, and they note that students -- not the school -- invited Sebelius.

The Obama administration mandate also has prompted 43 Catholic institutions - including Notre Dame – to file a civil suit that claims Sebelius violate constitutional protections of religious liberty. And at least two schools have stopped offering health insurance in part because of the financial impact.

Blatty said his efforts would follow a similar and “awesome” one in 1991 in which Georgetown students submitted a canon law petition.

“Georgetown’s Catholic identity was one of the many outstanding attributes that appealed to me,” he said. “Unfortunately, I found that Georgetown today lacks the integrity to consistently live the Catholic identity it claims.”