ST. PAUL — State Auditor Rebecca Otto said she’s appealing a controversial 2015 law limiting her office’s duties to the Minnesota Supreme Court.

Otto has lost several legal battles over the law that allowed counties to hire private firms for annual financial audits. The state Court of Appeals last month upheld a lower court’s ruling that the legislation was constitutional on a 2-1 decision.

Otto, a Democratic candidate for governor in 2018, had indicated she would appeal. She announced her formal appeal Thursday.

She said the law is an unconstitutional encroachment on her duties. Republicans who spearheaded the change say it helps counties save money.

Otto has spent more than $250,000 fighting the law so far.