ABS-CBN has filed a $1.5 million lawsuit accusing the media research company of releasing TV ratings from metered houses that had taken bribes.
Authorities have ordered AGB Nielsen to stop gathering data and releasing TV ratings for 20 days.
Eugenio Lopez, the ABS-CBN chairman, said: "We have discovered what can only be viewed as a systematic attempt to cheat the ratings system."
AGB Nielsen claims GMA staff bribed metered households in Bacolod City to influence ratings in the area. GMA denies this and has threatened to sue for libel.