MEMPHIS, Tenn. • Memphis police have followed labor organizers home after meetings, ordered fast-food workers not to sign petitions, threatened them with arrest and put some on a list requiring them to have a police escort when they visit City Hall, activists charge in a federal lawsuit.

The activists, who are pushing for higher wages and union rights at fast-food restaurants like McDonald's, sued the City of Memphis on Wednesday.

Lawyers with the Fight for $15 campaign's Mid-South Organizing Committee filed the federal civil rights lawsuit in U.S. District Court against the city, Mayor Jim Strickland and Police Director Michael Rallings.

Memphis' Chief Legal Officer Bruce McMullen said the city does not believe the lawsuit has merit.

The Fight for $15 campaign has been protesting in cities around the country since late 2012. It is seeking a $15-per-hour minimum wage. Protesters have been joined at rallies by other low-wage workers, such as home and child-care workers.

"They're trying to stop us from speaking out, but even though it's riskier, we know we have a right to protest and we're not going to be intimidated," said Ashley Cathey, a Church's Chicken worker, in a statement.