LANSING, Mich. (AP) — Michigan regulators on Friday demanded that one of the state’s biggest utilities, Consumers Energy, make tree trimming a bigger priority to prevent the sort of widespread and lengthy power outages caused by last winter’s ice storm.

The state Public Service Commission, in concluding an investigation into the December outages, said it was “unacceptable” for the Jackson-based utility to spend $16 million less trimming trees in 2013 than had been approved by regulators, the lowest amount since 2008. It said Michigan’s other major utility, DTE Electric, had shown a “strong commitment” to keeping up with tree trimming.