MEDFORD, Ore. (AP) -- It's union against union.

The workers who help the Oregon Education Association file grievances and negotiate new contracts went on strike Monday against the union they represent.

The OEA Professional Staff Organization, a union of 42 members, is upset about a proposed rollback in benefits. It also accused the OEA -- the state's largest teachers' union -- of unfair labor practices in a complaint filed with the National Labor Relations Board.

"It's never a happy time when you have to go on strike, but we also feel that if we don't stand up for our union how could we be trusted to stand up for others' unions?" Jane Bilodeau, a PSO member, told the Mail Tribune newspaper while picketing outside the OEA's Medford office.

Workers such as Bilodeau help OEA members in contract talks, assist in teacher complaints, arrange arbitration between teachers and their employers and publish newsletters about changes that could affect members.

Their two-year contract expired in July. In mid-August, the OEA presented the union with a "last-best offer" that included an annual 4 percent cost-of-living pay raise, but scaled back medical and retirement benefits.

Besides objecting to the reduced benefits, the union claims the OEA tried to strong-arm it into agreeing to terms before negotiations and refused to provide medical insurance claim information the union needed to craft a counterproposal.

BethAnne Darby, OEA director of public relations, says no information was withheld from the bargaining team.

"We are open to returning to the table to resolve the issues," Darby said. "We want the staff working with us, and we are sorry this is their choice, that they decided to go on strike."

The OEA has 48,000 members, including teachers, school support staff members and college employees.