State Insurance Commissioner Steve Poizner on Friday rejected an insurance industry recommendation for a 28 percent increase in workers’ compensation premiums, saying insurance carriers could do more to control costs.

While acknowledging that medical costs for workers’ compensation claims are rising, Poizner said insurance companies have not implemented many of the cost-saving measures in the 2004 reforms passed by Gov. Arnold Schwarzenegger and the Legislature.

“Once again, workers’ compensation insurers have failed to demonstrate that they have adopted procedures to control costs or that they are operating efficiently,” Poizner said. “It’s easier for the insurers to get together and argue that they need huge rate increases than for them to do the hard work of implementing cost savings.”

In recent years, the average rate increase has been 3 to 4 percent, the commissioner’s office said.

In summer, the Workers’ Compensation Insurance Rating Bureau, an industry group, recommended a 28 percent increase in basic workers’ compensation premium rates, citing rising medical costs and recent court rulings that give more latitude to doctors to prescribe expensive treatments for workplace injuries.

Gov. Arnold Schwarzenegger wrote a letter to Poizner urging him to reject the rate increase request, saying such a steep hike would hurt employers and force layoffs.

Poizner’s rejection isn’t binding. However, companies have generally respected his office’s stance because the state commission has authority over in other areas and the companies don’t want a hostile reception when they have business before the commission.

Companies will submit individual filings detailing and justifying their rate hikes to the commission.