PORTLAND – A longtime partner with one of Maine’s largest and most prestigious law firms has agreed to plead guilty to two counts of felony theft for stealing money from clients and the firm.

John Duncan, 54, was fired from Portland’s Verrill Dana law firm last year after being accused of stealing more than $300,000 over a 10-year period.

In a plea agreement, Duncan will waive an indictment and proceed directly to a plea hearing next Tuesday, Assistant Attorney General Mike Colleran told the Portland Press Herald.

Colleran wouldn’t go into specifics of the agreement, including possible restitution or what sentence he will recommend to the judge. Each count is punishable by up to 10 years in prison, but sentences in similar theft cases are generally less than three years.

Duncan’s attorney, Toby Dilworth, said his client will plead guilty to the charges.

“John wants to apologize to the firm and to his former clients. He is deeply remorseful,” Dilworth said.

Duncan worked at Verrill Dana for 29 years, handling wills, estates and trusts. He earned a reputation as a dignified and talented lawyer who was devoted to family and active in his church and philanthropic organizations.

Last year, a legal secretary reported that Duncan had written several checks to himself from the account of an elderly client. A subsequent audit uncovered other irregularities. Duncan was fired in November.

In all, Duncan allegedly stole $109,000 from clients and embezzled $196,000 from the firm, said Gregg Ginn, a partner at Verrill Dana who has been acting as the firm’s spokesman. Duncan also was accused of overbilling clients more than $100,000 over the years, but that’s not included in the criminal charges.

Duncan is also facing professional discipline. The state board that oversees lawyers’ conduct has passed the case to the Maine Supreme Judicial Court, which is the only court that can suspend or disbar a lawyer.

Duncan has submitted a letter of resignation from the bar, but it has not been accepted by the court.

“I am extremely sorry for my conduct. I am ashamed that I let down my family and my colleagues at the law firm,” Duncan wrote in the April 15 letter.