Microsoft Corp. is strongly opposing the National Labor Relations Board’s revised “joint employer” standard, saying in a friend-of-the-court brief in Washington that the agency’s approach could discourage companies from establishing corporate social responsibility programs.

A team from Orrick, Herrington & Sutcliffe, representing Microsoft and the HR Policy Association, filed the amicus brief Tuesday in the U.S. Court of Appeals for the D.C. Circuit in support of a company that is challenging the labor board’s standard. Some companies and business advocates fear that the revised standard could open a door to labor complaints from employees who are not under the direct control of a business.