WASHINGTON—Several business trade groups filed a lawsuit Monday to block the National Labor Relations Board’s new rule that would speed union-organizing elections, alleging the board overstepped its authority.

The plaintiffs alleged the rule adopted last month—one of the biggest procedural changes to the federal organizing process in decades—violates federal law, in part by curtailing an employer’s right to communicate with employees. The groups, which filed suit in U.S. District Court for the District of Columbia, say they collectively represent millions of employers and human-resource professionals at companies that would be subject to the rule when it goes into effect on April 14. The five plaintiffs include the U.S. Chamber of Commerce, the Coalition for a Democratic Workplace, the National Association of Manufacturers, the National Retail Federation, and the Society for Human Resource Management.

A divided NLRB adopted the rule on Dec. 12 in a 3-2 vote; the board’s Democrats supported the measure, saying it is intended to streamline union-organizing elections, while its two Republicans dissented. The rule drew backlash from businesses and congressional Republicans, who said it could deprive employers of time they need to tell workers why they think a company should remain union-free and limit their ability to launch timely legal challenges.

While the final rule didn’t establish a specific time frame in which union elections would occur, some legal experts have said the rule could shorten the time between a formal call for a union-organizing vote and the election itself to 25 days or less—almost two weeks short of the 2013 median of 38 days, or 59 days in contested cases. The plaintiffs said in their lawsuit that the rule would allow elections to be held in as little as 14 days after the employer is first notified of the election petition.

An NLRB spokeswoman declined to comment.

The plaintiffs allege the rule violates the National Labor Relations Act, the federal law the NLRB enforces in most private-sector workplaces. They said it wrongly restricts employers’ ability to litigate over such issues as whether certain employees are eligible to vote. The plaintiffs also said the rule “impermissible curtails” an employer’s right to communicate with employees by “substantially shortening” the period between an election petition and the election itself, calling it a violation of the First Amendment.

“The Board failed to meaningfully consider numerous legal, policy, and economic factors,” the plaintiffs said, calling the adoption of the rule an “arbitrary and capricious” action. The plaintiffs alleged that the NLRB failed to explain why the rule making was necessary, and said unions already win more than two-thirds of all representation elections.

“Unless vacated, held unlawful, and set aside, the Final Rule will adversely affect the rights of Plaintiffs and their members,” the lawsuit said.

The plaintiffs said while the vast majority of employees at companies affected by the rule aren’t represented by a union, there are active union organizing campaigns at many businesses. The plaintiffs said their members expect that employees at these businesses, or the unions that seek to represent them, will file election petitions soon after the rule becomes effective in April.