A legal complaint filed with the Federal Election Commission on Thursday accuses the Hillary Clinton campaign of illegally coordinating with David Brock’s super PAC.

The Campaign Legal Center charges that Brock’s PAC Correct the Record contributed nearly $6 million in in-kind donations to the Clinton campaign in the form of coordinated expenditures, Law Newz reported. Such donations are prohibited by federal law, according to the complaint.

Brock launched Correct the Record in 2015 to serve as a rapid response team for Clinton’s presidential bid. The PAC pledged to spend $1 million to "push back" against users posting negative comments about the Democratic nominee on Twitter, Facebook, Reddit, and Instagram.

The PAC boasted in April that its "Barrier Breakers" project had already "addressed more than 5,000 people that have personally attacked Hillary Clinton on Twitter."

The Campaign Legal Center said in its complaint the PAC publicly acknowledges its coordination with the Clinton campaign and charged that its multi-million-dollar operation is more extensive than a volunteer blogging movement.

"Correct the Record is a $6 million Washington D.C.-based political committee that spends millions on opposition research, message development, surrogate training and booking, professional video production, and press outreach for the benefit of the Clinton campaign—and by its own admission, does so in full coordination with the Clinton campaign," the Campaign Legal Center said in the complaint.

"Because Correct the Record is effectively an arm of the Clinton campaign, million-dollar-plus contributions to the super PAC are indistinguishable from contributions directly to Clinton–and pose the same risk of corruption," the group said in a statement.

Sen. Bernie Sanders criticized Clinton for hiring Brock as her lead super PAC operative in May, calling him "the scum of the Earth."