As America’s labor unions have lost members and clout, new types of worker advocacy groups have sprouted nationwide, and they have started to get on businesses’ nerves — protesting low wages at Capital Grille restaurants, for instance, and demonstrating outside Austin City Hall in Texas against giving Apple tax breaks.

After ignoring these groups for years, business groups and powerful lobbyists, heavily backed by the restaurant industry, are mounting an aggressive campaign against them, maintaining that they are fronts for organized labor.

Business officials say these groups often demonize companies unfairly and inaccurately, while the groups question why corporations have attacked such fledgling organizations.

The United States Chamber of Commerce issued a detailed report in November criticizing what it calls “progressive activist foundations” that donate millions of dollars to these groups, which are often called worker centers. The business-backed Worker Center Watch has asked Florida’s attorney general to investigate the finances of the Coalition of Immokalee Workers. That group sponsored a protest last March in which more than 100 workers marched 200 miles to the headquarters of Publix supermarkets to urge it to pay more for tomatoes so farmworkers could be paid more.