Updated

Two pro-business advocacy groups on Friday filed the first legal challenge to President Obama's recent recess appointments, asking a federal judge to find them unconstitutional.

The National Federation of Independent Business and the National Right to Work Foundation argue Obama cannot legally bypass the Senate to appoint three new members of the National Labor Relations Board, an agency that referees labor-management disputes.

The groups made the argument in a motion in federal district court in Washington, D.C., as part of an ongoing lawsuit against the labor board for requiring businesses to put up posters telling workers about their right to form a union.

The challenge came a day after the Justice Department issued a legal opinion defending the appointments of the labor board members, and the appointment of a national consumer watchdog, against Republican criticism.

Obama stoked controversy when he made the appointments Jan. 4 during the Senate's current 20-day recess. Republicans leaders have called it an unusual and unconstitutional power grab, saying the Senate was not technically in recess when Obama acted.

Neither the White House nor the NLRB had any immediate comment on the motion. But in the legal opinion released Thursday, the Justice Department argued the president has authority to make such appointments because the Senate is on a 20-day recess, even though it has held periodic pro forma sessions in which no business is conducted.

The department said the pro forma sessions -- some with as few as one member present -- have not been sufficient for the chamber to exercise its constitutional authority to advise and consent to normal presidential nominations.

Administration officials have said Obama made the appointments because Senate Republicans have been unfairly blocking Senate confirmation of nominees as a way to limit the power of agencies they oppose.

The NLRB is supposed to have five members, but it was down to only two until Obama acted. The agency is not allowed to conduct regular business with only two members.

On Jan. 4, Obama appointed Deputy Labor Secretary Sharon Block, union lawyer Richard Griffin and NLRB counsel Terence Flynn to fill vacancies on the five-member NLRB, giving it a full contingent for the first time in more than a year. Block and Griffin are Democrats, while Flynn is a Republican. Obama also appointed Richard Cordray, a former attorney general of Ohio, to be the first director of the Consumer Financial Protection Bureau.

In legal documents filed Friday, the pro-business groups argue the three new NLRB members are not legitimate because the U.S. Senate was still in session when they were appointed. The arguments come just days after NLRB lawyers officially notified the court that Obama's recess appointees were now parties in the ongoing legal dispute.

In their lawsuit, the groups question the legality of an NLRB rule approved last year. The board wants most businesses to display posters explaining the right to bargain collectively, distribute union literature and engage in other union activities without reprisal.

The rule has met with stiff resistance from business groups who call the language too one-sided in favor of unions.

"The rule can't be implemented and enforced without a functioning board," said Mark Mix, president of the National Right to Work Foundation. "We believe the validity of these appointments is in question."