DETROIT (Reuters) - A former Michigan prosecutor who had been an outspoken advocate for ending prostitution pleaded guilty on Tuesday to patronizing prostitutes and misconduct in office, the state's attorney general said.

Stuart Dunnings III, a former prosecuting attorney in central Michigan's Ingham County, was arrested in March and charged with 15 criminal counts, including felony pandering and multiple prostitution misdemeanors.

The majority of the charges were dropped under a plea deal announced on Tuesday in which Dunnings admitted guilt to a new felony charge of misconduct in office, Michigan Attorney General Bill Schuette said in a statement.

The misconduct charge carries a maximum sentence of five years in prison and a $5,000 fine, Schuette said. Dunnings also pleaded guilty to a charge of soliciting a prostitute, a misdemeanor, which carries a maximum fine of $500, Schuette said.

An attorney for Dunnings could not immediately be reached for comment.

The charges against Dunnings came out of a 2015 federal investigation of human trafficking and prostitution.

Schuette said Dunnings has been an outspoken advocate for ending human trafficking and prostitution, even as he allegedly used escort sites to find multiple prostitutes and pay for sex hundreds of times in three counties between 2010-2015.

Dunnings entered his plea before Judge Michael Klaeren of the 12th District Court in Jackson.

Dunnings served as chief prosecutor of Ingham County, which includes the state capital of Lansing, for close to two decades. He was re-elected in 2012 with nearly 70 percent of the vote.

(Reporting by Ben Klayman in Detroit; Writing by Eric M. Johnson in Seattle; Editing by Leslie Adler)