The chairman of Nippon Television Network Corp. on Monday resigned his posts at an industry self-regulatory body following revelations that an NTV producer paid viewers to manipulate ratings.

Seiichiro Ujiie, NTV chairman and chief executive officer, stepped down from all his posts, including chairman emeritus of the National Association of Commercial Broadcasters in Japan, which manages and enforces the TV and radio broadcasting code among private broadcasters.

Ujiie, 77, tendered his resignations during an emergency meeting of the association's policy board. His offer was accepted. "I am feeling responsibility as a corporate manager," Ujiie told a news conference.

On Monday, NTV set up an investigative task force and appointed Shuzo Ebata, former prosecutor general of the Supreme Public Prosecutors Office, as its chairman. The six-member group is expected to compile a report in about 10 days and submit it to both the broadcasting association and NTV.

On Friday, NTV revealed that a 41-year-old producer had used a credit research agency in Saitama Prefecture to identify 12 to 13 households involved in surveys by Japan's only TV ratings firm, Video Research Ltd. It said he asked them via a friend to watch at least six specific programs between July 2002 and September this year.