COLDWATER, Mich.—Proposed rules allowing meatpackers to slaughter hogs faster and play a bigger role in policing food safety are intended to free up government inspectors while making plants more efficient. But the rules, which could take effect this year, have drawn criticism.

Consumer advocates question whether companies can guarantee the cleanliness of their pork while workers take on some tasks previously reserved for U.S. Department of Agriculture inspectors. Meanwhile, worker-rights groups say speeding up slaughter lines...