The National Labor Relations Board announced on Friday that its general counsel had brought 78 charges against McDonald’s and some of its franchise operators, accusing them of violating federal labor law in response to workers’ protests for higher wages around the country.

The general counsel’s move immediately drew outrage from a variety of national business groups because the labor action deemed McDonald’s a joint employer, a status that would make the fast-food titan equally responsible for actions taken at its franchised restaurants.

The labor board’s complaint asserts that McDonald’s and numerous franchise operators in more than a dozen cities illegally retaliated and made threats against workers who had joined national protests pushing for a base wage of $15 an hour in the nation’s fast-food restaurants.

Business groups vigorously attacked the general counsel’s complaint, saying that it was wrong to consider McDonald’s a joint employer and seek to hold it jointly responsible for the actions of its franchise operators. The labor board’s complaint, if successful, could disrupt many longtime practices in the fast-food industry — as well as other industries — and ease the path for unionizing fast-food restaurants nationwide.