The National Labor Relations Board member facing questions about his previous gig as a lawyer representing a union with criminal ties distanced himself this week from the incidents, saying, "at no time did I serve as counsel" on those cases.

Board member Richard Griffin responded in a letter Monday to Utah GOP Sen. Orrin Hatch, who has led an effort to learn more about Griffin's 17 years as general counsel for the International Union of Operating Engineers.

Hatch and others have made clear that they never thought Griffin represented members in criminal cases. However, they wanted his on-the-record responses in large part because President Obama in January made him a recess appointment to the board, which avoided a Senate vote.

In the four-page letter Monday, Griffin said he made every effort to ensure union officials fairly represented their 400,000 members. And in "rare instances" of malfeasance in local unions, Griffin said, he worked closely with top IUOE officials to "remove the offending officials and put in place practices and procedures to guard against any recurrence."