The nation's only TV ratings firm filed a damages suit Thursday against a former Nippon Television Network Corp. producer over his manipulation of ratings through the use of illicit funds.

Tokyo-based Video Research Ltd. wants Masafumi Ando to pay about 91 million yen in damages for harming the credibility of its viewer ratings surveys.

The scandal at the broadcaster surfaced last year, shocking the TV industry. Manipulating ratings had been unheard of in Japan.

In its suit filed with the Tokyo District Court, Video Research claimed that between March 2000 and July 2002, Ando identified 18 households involved in the surveys and asked them to watch his NTV programs.

It alleged that he paid bribes, including gift certificates of about 10,000 yen, to households that agreed.

Investigations by a fact-finding team commissioned by NTV found that Ando misused 10.08 million yen earmarked for production expenses to manipulate TV ratings. He was fired in November.

Video Research did not sue NTV because the report found no evidence that the broadcaster was engaged in systematic manipulation, and concluded that the scheme involved only Ando.