Congressional Republicans vowed Wednesday to "push back" against the Obama administration after the Labor Department issued a rule change that will benefit union organizing campaigns.

The American Bar Association also said it remained opposed to the new rule, arguing that it would undermine attorney-client privilege.

The new rule will force management-side labor law firms to publicly divulge all of their activities, including the financial details, a requirement that will likely force many of them out of consulting. Previously, the disclosure was required only if the lawyers had direct contact with their client's employees, for example, if they were hired to directly argue to employees that they should not join a union. Now, firms that advise managers privately on what federal labor law requires must disclose all details as well.

House Education and the Workforce Committee Chairman John Kline, R-Minn., and Health, Employment, Labor, and Pensions Subcommittee Chairman Phil Roe, R-Tenn., slammed the rule change in a joint statement, saying it would "stifle ... debate and undermine the ability of workers to make a fully informed decision."

"This rule will chill employer free speech and make it harder for small business owners to navigate a host of complex labor rules. ... The administration has made it clear they're not interested in fair or democratic union elections. They're interested in tilting the balance of power toward union interests — no matter the costs," the lawmakers said.

Sen. Lamar Alexander, R-Tenn., chairman of the Senate Health Education, Labor and Pensions Committee, was also critical. "Instead of rolling out policies that seem intended only to boost organized labor, the Labor Department should instead focus on ways to grow our economy and get more Americans back to work," he said

The lawmakers vowed to "push back against this rule" but offered few details on what that would entail. Since the rule change is technically a reinterpretation of the Labor Management Reporting and Disclosure Act, congressional approval is not required.

American Bar Association spokesman Matthew Cimento said the group had "no official comment" Wednesday but pointed to statements issued by the association in 2011 when the administration proposed the rule change. Then-ABA President Bill Robinson warned at the time that the proposed change would "seriously undermine both the confidential client-lawyer relationship and the employers' fundamental right to counsel."

"Our reasons for opposition ... have not changed," Cimento told the Washington Examiner.

Labor groups cheered the administration's announcement. "It takes great courage for working people to come together to form a union. Working men and women deserve to know who their employer is hiring and exactly how much they are spending to discourage workers from forming a union," said AFL-CIO President Richard Trumka.

The Labor Department signaled that it was going to rewrite the rule in 2011, and it was initially set to be released in 2014, but it was delayed until this year. Many labor lawyers speculate the administration was trying to craft a version that would withstand legal challenge. The new version will be officially published Thursday in the Federal Register and go into effect July 1.

Previously, labor lawyers hired as consultants by businesses facing union organizing campaigns had to divulge their activities only if the lawyers had direct contact with the workers. Law firms that merely advised managers on what to do or the finer points of the law were exempted.

Labor leaders had long decried this as a "loophole," since management-side lawyers often gave managers scripts to work from. In a statement Wednesday announcing the change, Labor Secretary Tom Perez agreed, also referring to the exemption as loophole.

Business groups have countered that the new rule requires disclosure even when the law firm is merely explaining federal labor law and its requirements to business owners who have never had to deal with it before. Medium- and small-sized business will find it harder to get advice under the rule since many lawyers will decide it is not worth the disclosure. Larger firms that service big business are not expected to be affected since most were already disclosing under the old rule, management-side lawyers say.

Joshua Parkhurst, a New York union-side labor lawyer, said he understood the concern regarding attorney-client privilege, but added, "Many management-side law firms explicitly advertise their skills in 'union avoidance' campaigns. And their work goes well beyond giving legal advice or ensuring legal compliance."