Federal lawsuits alleging that U.S. employers violated the Fair Labor Standards Act are up more than 30 percent in the past five years, and both state and federal labor officials are bringing more actions charging that employers violated minimum wage and overtime rules or avoided payroll taxes by improperly classifying employees as outside contractors.

Employment attorney Steven Harz, of Archer & Greiner, in Hackensack, said the federal government "has made it clear that it wants to increase the number of people who are deemed employees versus independent contractors." He said he represents more than 40 New Jersey employers in cases where labor law violations are alleged.

Harz said he advises employers to review their work force every quarter to make sure outside contractors have been properly classified. If the employer "is supervising, directing or controlling the exercise of the services provided by these outside individuals, the state or federal department of labor can (seek to establish) that the individual is an employee, with all the required taxes and deductions."

Harz said he often is able to make the case that the contractors were classified properly, but said employers who are vigilant can avoid the legal and administrative expense of these lawsuits.

According to the state Department of Labor, audits of employers conducted by the agency identified underreported taxes of $27.2 million in 2011, up from $25.2 million in 2010, $20.9 million in 2009 and $18.3 million in 2008.

Josh Weiner, an employment attorney with Weiner & Weiner, in Morristown, said many employers don't realize that undocumented immigrants can go to court for back wages under the federal and state labor laws, despite being in the country illegally.

"The courts are very protective of them, and don't allow immigration status to be an issue," Weiner said. The rationale is that otherwise employers would have an incentive to hire undocumented workers. "The employers say, 'But we're doing these people a favor, because otherwise they would not be able to work.' But in the end, you have to abide by the wage and hour laws," Weiner said.

His partner, Paul Weiner, said wage and hour cases are prevalent in the restaurant and hospitality industries, but can be found throughout the economy. "Often, small employers don't understand the law, and we need to get the message out that employers should be checking how they employ and pay people."