WASHINGTON — The Labor Department on Wednesday released the final version of a rule requiring employers to disclose relationships with the consultants they hire to help persuade workers not to form a union or support a union’s collective bargaining position.

The department said the rule, which will be published on Thursday and apply to agreements made after July 1, is necessary because workers are frequently in the dark about who is trying to sway them when they exercise their labor rights.

“In many organizing campaigns, decisions that workers make about whether to choose to stand together are often influenced by paid consultants, or persuaders, who are hired by employers to craft the management message being delivered to workers,” Labor Secretary Thomas Perez said in a call with reporters. “About 75 percent of employers hire such persuaders, and too often, workers do not know.”

The 1959 law on which the regulations are based already required employers to disclose the hiring of such consultants. But the Labor Department argued that previous administrations had allowed an enormous loophole that effectively exempted consultants who coached supervisors on how to influence employees so long as the consultants didn’t interact with the employees directly.