A trial-lawyer-backed initiative that would roll back most of the workers’ compensation reforms enacted three years ago has qualified to begin collecting signatures, Secretary of State Debra Bowen announced Thursday.

The initiative, put forward by workers’ compensation plaintiff attorney William Morris, would reinstate the unlimited right of an injured worker to choose his or her own doctor, eliminate the right of employers to challenge treatment and diagnostic evaluations, and eliminate the need for most pre-approvals for medical treatment of injured workers.

Business groups led by the California Chamber of Commerce already have formed a coalition to campaign against the measure, claiming it would cost employers billions of dollars each year in additional workers’ compensation premiums and medical costs.

Attorney General Jerry Brown, in his summary of the proposed ballot measure, estimated that passage of the measure would cost state and local governments hundreds of millions of dollars in additional workers’ compensation benefit payouts.

Since two sets of workers’ comp reforms were enacted in 2003 and 2004, employer premiums have plunged more than 50 percent, saving employers several billion dollars annually. Earlier attempts by organized labor and trial attorney groups to roll back some of the reforms have either failed to gain legislative approval or were vetoed by Gov. Arnold Schwarzenegger.

The initiative proponents must collect 433,971 signatures by Sept. 10 to qualify the measure, which would then appear on a statewide ballot early next year.