The National Labor Relations Board set an April 5 union election date at Kaiser Permanente, where the representation of more than 45,000 California employees is at stake.

NLRB officials ordered a new election after the National Union of Healthcare Workers challenged the results of an October 2010 election. The complaint alleged that Oakland, Calif.-based Kaiser favored SEIU-United Healthcare Workers West, which won 61% of the vote. Kaiser has said the system has no preference for either union.

Employees will cast their votes via mail with an April 29 deadline. NLRB officials at the agency's regional office in Oakland will start counting the ballots on May 1.

SEIU officials on Monday continued to express confidence in winning the election.

NUHW, whose leadership is made up of ex-SEIU members, meanwhile, continued their attacks on SEIU, saying the contracts SEIU has bargained with Kaiser provide too many concessions, and that the union has been too cooperative with Kaiser management. Kaiser owns 30 hospitals in California.

A win could be significant for NUHW, which represents 10,000 workers in California, including 4,000 at Kaiser hospitals. Last month NUHW formed an affiliation with the California Nurses Association and described the partnership as a bid to compete more forcefully with SEIU for workers. NUHW and CNA combined have about 95,000 members in California. SEIU, however, represents about 150,000 healthcare workers in the state.