WASHINGTON — Frustrated with union-friendly decisions from the National Labor Relations Board (NLRB), Republicans hope to cut off the agency's power by denying President Obama the chance to name members while the Senate is in recess.

The five-member board is now down to three members, and another will leave at the end of the year. The remaining two members could not legally issue decisions or make new rules.

"What they would be doing quite explicitly is trying to keep an agency from functioning through this maneuver," said former board member Wilma Liebman, a Democratic appointee whose term ended in August.

For months, House Republicans have convened brief, pro forma sessions whenever Congress is away to prevent the Senate from going into a full recess. The tactic has kept Obama from using recess appointments to bypass the Senate to name members of the labor board, choose a new chief of the Consumer Financial Protection Bureau and appoint other officials unlikely to win Senate confirmation.

The labor board is a lightning rod in the ideological war between businesses and unions over the right of workers to organize. But the long-simmering conflict has boiled over this year. Republicans say the board has taken unprecedented steps that are unacceptable to business.

The board has proposed new rules that would speed up union elections, giving employers less time to counter organizing drives. It also decided to let smaller groups of workers try to form unions, which could make it easier for unions to gain a foothold in some companies.

The most high-profile outrage for Republicans, though, is a complaint filed earlier this year against Boeing by the NLRB's acting general counsel. The complaint accuses the company of illegally retaliating against unionized workers in Washington state by opening a new plant in South Carolina, a right-to-work state where labor unions' power is limited.

Republicans call the Boeing complaint an unfair government intrusion into a legitimate business decision. Last month, the GOP-controlled House passed legislation that would undercut the Boeing case by stopping the NLRB from ordering an employer to shut down plants or relocate work, even if a company violates labor laws. But the measure is going nowhere in the Democratic-run Senate.

From 2008 to 2010, the labor board endured a record 27 months when it had too few members to operate. Senate Democrats had refused to fill vacant seats during Bush's final year in office, angered by a series of pro-business rulings. Then it was Senate Republicans' turn to stall when Obama sent up his own nominees, deemed too sympathetic to labor.

During that time, the board's two members, one Democrat and one Republican, decided cases on which they could agree and postponed — sometimes for years — those on which they couldn't. But the Supreme Court ruled last year that two members were not enough to decide any case before the board.

Obama finally made two recess appointments in March 2010, including Craig Becker, a former union lawyer whose views Republicans considered too radical. Becker's recess appointment will expire at the end of this year, and Republicans have made clear they will block an effort to confirm him through the regular nomination process.

Without a quorum of three members, NLRB staff members can still carry out the agency's core functions, such as issuing complaints, investigating labor-law violations and overseeing union elections. About 95 percent of cases are resolved without ever being appealed to the five-member board.

But the board still hears appeals on hundreds of cases each year, some of which can lead to new policies or change existing case law. Democrats warn that businesses caught violating labor laws could simply appeal their cases to delay fines and penalties, knowing they would never be heard while the board lacks a quorum.

It could also prevent the board from ruling on the Boeing case. The action is now being heard by an administrative law judge in Seattle, but any ruling would not be effective until the full board ruled on appeal.