The rulings of the National Labor Relations Board have poured out one after another in recent months, with many decisions tilting in favor of employers.

The Republican-dominated board has made it more difficult for temporary workers to unionize and for unions to obtain financial information from companies during contract talks. It has ruled that graduate students working as teaching assistants do not have the right to unionize at private universities, and it has given companies greater flexibility to use a powerful antiunion weapon - locking out workers - in labor disputes.

And in a decision that will affect 87 percent of American workers, the board has denied nonunion employees the right to have a co-worker present when managers call them in for investigative or disciplinary meetings.

The party-line decisions have been applauded by the Republican Party's business base, which sees them as bringing balance after rulings that favored labor during the Clinton administration. But some academic experts on labor relations say the recent rulings are so hostile to unions and to collective bargaining that they run counter to the goals of the National Labor Relations Act, the 1935 law that gave Americans the right to form unions.

"These decisions come close to or even match the Reagan board in their intensity and vigor in promoting employer powers," said James A. Gross, a professor at Cornell University who has written several books about the board. "They are pressing the outer limits of what could be a reasonable or legitimate interpretation of the balance between employer prerogatives and worker rights. In my mind, this is fundamentally inconsistent with the purpose of the National Labor Relations Act, which is to encourage the practice and procedures of collective bargaining."

Robert J. Battista, the labor board's chairman, denied that the panel was stretching the law to help corporations.

"All the cases that we've decided have been well reasoned," Mr. Battista said. "They're certainly consistent with the act. I wouldn't characterize them as pro-business or pro-union. I'd like to say they're pro-employee."

The board's defenders say it is merely continuing a long tradition of swinging back and forth: toward management when a Republican is in the White House and toward labor during Democratic presidencies.

"After eight years of a liberal Clinton board and an extremely liberal general counsel, there is of course going to be some turning back toward a conservative agenda," said Randel Johnson, vice president for labor, immigration and employee benefits at the United States Chamber of Commerce. "The board has turned a corner here, but it's not a wholesale reversal of the case law in favor of the business community."

Several recent board decisions, Mr. Johnson pointed out, have reversed Clinton-era rulings that overturned precedents set by Republican boards. In a case involving I.B.M., the board voted 3 to 2 to overturn a Clinton board ruling that gave nonunion workers the right to have a colleague accompany them to investigative or disciplinary meetings with supervisors. The Clinton-era ruling was a reversal of a 1980's decision.

In a case involving Brown University, the board reversed a Clinton-era ruling involving New York University - a reversal of a 1970's decision - that gave graduate student teaching assistants the right to unionize.

Mr. Battista said, "What we did restores the precedent that has been time-honored and had never been overturned by a court or by Congressional action."

Labor unions say the reversals will make it much harder to organize workers at a time when the percentage of Americans belonging to unions is declining.

Jonathan Hiatt, the general counsel for the A.F.L.-C.I.O., said, "The notion that in 15 or 20 recent cases the Republican majority has changed board law in ways that take away worker rights, deny workers protection in organizing and collective bargaining, and give employers more latitude, that is really striking and very political."

The labor board has five seats, and the president appoints members to five-year terms. For much of 2004, Republicans had a 3-to-2 majority, but two members stepped down in December, resulting in a 2-to-1 Republican majority until the seats are filled.

Unions are alarmed by the board's decision to hear several cases that question the legitimacy of card checks, one of labor's most successful tactics in adding members recently. In the procedure, companies agree to grant union recognition after a majority of workers sign cards saying they want a union. By agreeing to card checks, companies waive the right to hold a secret ballot to determine whether workers favor organizing.

With pro-business groups saying union organizers sometimes intimidate workers, Mr. Battista said, it was time to take a critical look at card checks.

But the board's Democratic members vigorously objected. "The issues raised by the petitioners were settled 40 years ago," they wrote. "To revisit it serves no purpose but to undermine a principle that has been endorsed time and again by the board and the courts."

Many unions say unionization elections are less fair than card checks because they involve expensive and bitter campaigns in which companies often fire and intimidate union supporters and warn that plants may close if they become unionized.

Charles Craver, a professor of labor law at George Washington University, said the board's conservative tilt would hurt unions, but less so than the conservative tilt of the federal judiciary, which he said was increasingly unfriendly to labor.

"I think we have a labor board as conservative as any time since the Reagan board," Professor Craver said. "It really troubles me because we're revisiting a lot of cases that have been fairly well settled."

In October, the board upheld a company's decision to fire a worker who had asked a colleague to testify before a state agency to support her claim of sexual harassment by a manager. The National Labor Relations Act prohibits employers from retaliating against workers who engage in concerted activity for mutual protection, but the board found that the fired woman was acting only in her interests and not for mutual protection to safeguard other workers from harassment.

"Taken one by one, I do not think these are the kinds of decisions that make one sit back and say, 'This is outrageous,' " said Theodore St. Antoine, an emeritus professor of labor law and former dean of the University of Michigan Law School. "At the same time, I have to concede that once more we're in the nibbling process. While none of them consist of a great big bite, the cumulative effect is to decrease the capability of unions to organize."

In September, in a case involving a trucking company that said it was "in distress" and "fighting to stay alive," the board ruled that such claims did not trigger an obligation for management to furnish financial information to the union. Traditionally, when companies in contract talks say they cannot afford what the unions are seeking, they are required to provide information detailing their financial condition.

The same month, the board ruled that disabled janitors could not join a union with able-bodied janitors, on the grounds that the disabled workers' relationship with their employer was "primarily rehabilitative" and not a traditional employee-employer relationship.

"We haven't got a particular agenda," Mr. Battista said. "Nor are we attempting to press the outer limits of management rights. We're trying to strike a balance between union rights, management rights and employees' rights."