MANCHESTER, N.H. -- A New Hampshire priest who was the former leader of one of the nation's top clergy treatment centers was sentenced Wednesday to serve at least four years in prison for stealing $300,000 from a hospital, a dead priest's estate and the state's Roman Catholic bishop.

Monsignor Edward Arsenault held several senior positions in the New Hampshire diocese from 1999 to 2009, when he became president and CEO of Saint Luke Institute in Maryland. He resigned in May after allegations arose involving an inappropriate adult relationship and misuse of church funds.

Details of the thefts revealed Wednesday show a priest who billed the church for lavish meals and travel for himself and often a male partner. He was convicted of writing checks from the dead priest's estate to himself and his brother and billing Catholic Medical Center $250 an hour for consulting work he never did.

"It's criminal behavior. It's disturbing behavior," Senior Assistant Attorney General Jane Young said. "These are thefts from a charitable institution by someone very high up."

Arsenault pleaded guilty in Hillsborough County Superior Court Wednesday to three felony theft charges. He stole $104,000 from Catholic Medical Center in Manchester by submitting false invoices and working only a third of the hours called for in his consulting contract, which ran from March 2009 until June 2010.

Young said Arsenault stole $184,000 from then-Bishop John McCormack and the Manchester diocese by billing for meals at some of Boston's finest restaurants. He also purchased cellphones and computer equipment, among other expenses. Young said he submitted fake invoices for about $15,000 in psychological counseling he never received.

Young said Arsenault stole $23,000 as executor of the Monsignor John Molan's estate in 2010, including an $8,000 check he made out to his brother.

The investigation did not involve Saint Luke Institute, a prominent education and counseling center based in Silver Spring, Md., with sites in other parts of the U.S. and in Britain. The center treats priests with a range of mental illnesses and has played a key role in addressing the problem of sexually abusive clergy.

Before he was sentenced, Arsenault apologized to "the many people I have harmed, including the priests and the faithful."

"Today is only the beginning of the consequences of my criminal behavior," Arsenault said.

Arsenault was sentenced to four-to-20 years, including a deferred, two-year sentence that the judge has the option to tack on when Arsenault returns to court after the four years are up. He was also ordered to pay $300,000 in restitution.

As he was escorted from the courtroom, his hands cuffed behind his back, he paused briefly in front of the prosecution table and awkwardly extended a handshake to Young.

His attorney, Cathy Green, told Hillsborough North Superior Court Judge Diane Nicolosi, Arsenault "was the person who held the diocese together" during the priest sex abuse scandals a decade ago. She called his prison sentence "significant."

Arsenault had been McCormack's top lieutenant, handling both the clergy sexual abuse crisis and orchestrating the church's new child protection policies. Bishop John Libasci, in a statement issued on behalf of himself and McCormack, said Arsenault stole more than money.

"Many of the faithful and former co-workers inevitably will be left with a profound sense of betrayal and mistrust," Libasci said.

CMC President Joseph Pepe said the hospital is saddened by Arsenault's criminal conduct, but relieved that Arsenault is being held accountable.

Young said the investigation began last year, after church officials and parishioners came to the attorney general's office and said they suspected large sums of money had been misappropriated. She stressed that Arsenault cooperated fully and will continue to cooperate as investigators look into whether anyone else was involved.