Every year, U.S. employers spend millions of dollars on outside consultants who specialize in breaking up union campaigns. Because much of that work is cloaked in secrecy, progressive groups are urging the Biden administration to crack down and make it more transparent.

A paper released in May by the Harvard Center for Labor and a Just Economy recommends that the Labor Department force employers and their consultants to make greater financial disclosures related to anti-union spending so workers can better understand who’s being paid to lobby them. The authors write that the firms are “deploying increasingly aggressive tactics to dissuade employees from unionizing.”