“Our wages are already at rock bottom,” Sharnell Grandberry, a McDonald’s worker in Detroit, said in a news release announcing the suit. “It is time for McDonald’s to stop skirting the law to pad profits. We need to get paid for the hours we work.”

A McDonald’s spokeswoman released this statement: “McDonald’s and our independent owner-operators share a concern and commitment to the well-being and fair treatment of all people who work in McDonald’s restaurants. We are currently reviewing the allegations in the lawsuits. McDonald’s and our independent franchisees are committed to undertaking a comprehensive investigation of the allegations and will take any necessary actions as they apply to our respective organizations.”

In three lawsuits brought in California, the workers claim that the McDonald’s restaurants employing them did not pay them for all hours worked, shaved hours from pay records and denied them required meal periods and rest breaks.

The lawyers are contending that McDonald’s should be considered a joint employer and share liability with its franchisees, although the company, like many other fast-food chains with franchises, has argued in the past that it is not a joint employer and should not be liable for its franchisees’ misdeeds on the ground that the franchised restaurants are independently run businesses.

The strategists behind the push for a $15 wage, which is largely financed by the Service Employees International Union, are trying to pressure McDonald’s and other fast-food chains to increase wages and not oppose union-organizing efforts. The movement began with several one-day strikes in New York in 2012 and expanded to one-day strikes in more than 70 cities last December.