NEW YORK, NOV. 17 -- Dun & Bradstreet Corp. said today it is terminating its proposed acquisition of Information Resources Inc. in light of the Federal Trade Commission's decision to oppose the merger on antitrust grounds.

The FTC announced late Monday in Washington that it is seeking a preliminary injunction blocking the acquisition on grounds the merger could substantially reduce competition in syndicated national tracking services, which are methods of tracking what products consumers buy.

Dun & Bradstreet and IRI are two of the three companies that provide such services. The third is SAMI-Burke Inc., a subsidiary of Time Inc.

Dun & Bradstreet, a leading business research and information concern, announced a definitive agreement to acquire Chicago-based IRI on Aug. 27 in a stock transaction then worth about $570 million.

Since then, the decline in Dun & Bradstreet's stock from $67 a share to $53.25 at Monday's close slashed the value of the deal to about $455 million. IRI shares closed today at $13, down $8, while Dun & Bradstreet closed $52.62 1/2, down 62 1/2 cents.

Dun & Bradstreet provides marketing research services through its Nielsen Marketing Research Division, which includes the Nielsen Media Research division, which rates audience share of television programs.

IRI's BehaviorScan service, its key product, is an electronic market research system that uses supermarket scanners to measure what people are buying in a specific region.

IRI had stated late Monday in Chicago that it had been notified the FTC would seek a court order blocking the transaction today, and the company did not intend to oppose the action.

The company said its former top management, which planned to take positions with Nielsen Information, would return as the management team of IRI