The union representing nurses at the Washington Hospital Center went to court this week to prevent the hospital from replacing an existing pension plan with a plan the union says is more expensive for workers and less secure.

The D.C. Nurses Association, which represents 1,200 registered nurses at the Hospital Center, filed suit in federal court and at the National Labor Relations Board, seeking an injunction preventing the hospital from terminating or modifying the existing pension plan.

The union said establishment of the new plan would violate provisions of its collective bargaining agreement that requires the hospital to maintain benefits "at least at current levels."

Separately, the president of the union representing 1,600 service workers at the Hospital Center said yesterday that his group intends Monday to file a grievance with the hospital and a complaint with the NLRB about the pension issue. Marchel Smiley, president of Local 722 of the international service workers union, said the hospital's unilateral plans to establish the new plan violates the workers' contract.

The Hospital Center, an 821-bed facility in Northwest Washington, recently disclosed plans to terminate its employe pension plan on July 1. The center said it would transfer the funds to a new plan being set up for employes of the entire Medlantic Health Care Group, the nonprofit holding company for the center and several other health facilities in the area.

Medlantic has argued that the new plan will be administratively easier to handle, will return higher benefits and will permit employes to stay in the same pension plan as they move throughout the system. Medlantic employes are covered by several plans now, a spokeswoman said.

The spokeswoman for Medlantic declined comment on the lawsuit yesterday, but said: "The objective of Medlantic and member hospitals has always been to provide appropriate benefits to employes. Seeking to meet that objective was the purpose of offering a new pension program to Washington Hospital Center Employes."

But Mary Joyce Carlson, an attorney for the nurses association, said the new plan is filled with problems for members of her group, including the hospital having sought to impose the plan unilaterally and without bargaining with the union.

The 350 nurses in the existing plan must contribute $52 a year to the pension fund, while under the new plan they must contribute 1 percent of their salary, which could amount to between $240 and $415, according to the lawsuit.

The nurses association estimates that there is $30 million in the hospital's pension plan, or about three times what is needed to pay off what is owed. In essence, she said, Medlantic is using the hospital employes' money to subsidize other workers' pensions. "The payment is better under the new plan, but the payment is not what it should be, given what is in the fund," she said.