Scott Harshbarger, now at the firm Proskauer Rose, has also served as head of Common Cause, which advocates open government, The New York Times reported.
The Association of Community Organizations for Reform Now announced last week it was conducting an internal review of its operations. The group is refusing new clients for its counseling program on tax, housing and benefits.
ACORN is under investigation in several states. Some of the investigations were prompted by a conservative activist, James O'Keefe, posing as a pimp who secretly videotaped sessions with ACORN tax advisers, while other investigations arose from allegations of fraudulent voter registrations.
The Maryland attorney general's office announced an investigation Monday into the organization's Baltimore operations. A spokeswoman promised a broad investigation but was unsure if it would include whether O'Keefe violated state laws on unauthorized recordings.
O'Keefe has worked with anti-abortion activist Lila Rose, who posed as an underage pregnant teen to catch Planned Parenthood employees agreeing to skirt state laws requiring reporting of statutory rape. Televised reports based on his recordings suggest some ACORN employees were willing to advise him on getting tax credits for a sex business.