The Casper-based True Companies illegally paid some of their female accounting clerks less than male employees for doing the same jobs, according to a lawsuit filed in federal court on Friday.

"Defendants unlawfully have withheld and are continuing to withhold the payment of wages due to the women employed as Accounting Clerk," according to the lawsuit filed by the Wyoming U.S. Attorney's Office and the Phoenix office of the EEOC.

"Defendants have a long history in business which has acquainted them with the obligations imposed by law with respect to state and federal statutes regulating pay to their employees," according to the lawsuit.

The federal government named these True Companies as defendants: True Oil LLC, Belle Fourche Pipeline Company, Black Hills Trucking, Inc., Bridger Pipeline LLC, Butte Pipe Line Company, Eighty-Eight Oil LLC, Equitable Oil Purchasing Company, Toolpushers Supply Co., True Drilling LLC, and True Ranches LLC.

True Companies' chief legal counsel did not return a call seeking comment.

The companies operate as "single integrated enterprise" with "interrelated operations, common management, central control of labor relations, and common ownership or financial control," according to the lawsuit.

Dave True and Hank True manage all the businesses, and all the accounting operations operate in the same complex at 455 N. Poplar St., according to the lawsuit.

The companies' controller, Dwayne Parks, made decisions regarding raises and promotions for the accounting departments of all the businesses. The same employee handbook was distributed to all the employees, too, according to the lawsuit.

Since May 2010, the True Companies have employed at least 37 people as accounting clerks who have done substantially the same work using the same skills and under similar conditions.

But the True Companies have paid and continue to pay the women less than the men, according to the lawsuit.

For example, the companies in 2002 hired a man who had taken one accounting course, had one year experience as a para-professional for an accountant, and 11 years of experience as a store manager which included bookkeeping as one of his responsibilities.

True Companies hired one woman in 2004 who had an associate's degree in accounting and 17 years of experience working with general accounting jobs. In 2004, the companies hired another woman who studied accounting for two years after receiving her high school diploma, and who had operated her own business for 10 years and had five years of bookkeeping experience.

The EEOC tracked the pay rates for four years. In 2013 alone, the man was paid $4.07 more an hour than the first woman, and he was paid $3.09 more an hour than the second woman, according to the lawsuit.

The True Companies alleged equal pay violations go beyond discrimination, according to the lawsuit.

At least two of the companies have been federal contractors with signed agreements with the federal government stating they will comply with federal law regarding equal pay.

"As a result of their long history as employers and their experience as federal contractors with attendant commitments to comply with federal law, Defendants could not have failed to comply with the requirements of the EPA (Equal Pay Act) without knowledge and accordingly, the unlawful practices ... were and are willful," according to the lawsuit.

The EEOC is asking the court for a permanent injunction to stop the True Companies from engaging in wage discrimination, and ordering them to quit paying wages to employees of one sex at rates less than the opposite sex for equal work.

It wants the companies to institute and implement polices to provide equal employment opportunities for women and remedy the effects of their illegal employment practices.

And the EEOC wants the court to order the True Companies to pay appropriate back wages and other financial relief.

Efforts to resolve the dispute were in vain, according to the lawsuit. "Even though it was not required to do so, the EEOC endeavored to eliminate the alleged unlawful employment practices by conciliation but was unable to secure a conciliation agreement acceptable to the Commission."