The French Foreign Ministry formally denied today a U.S. Defense Department official's charges that France had signed a secret agreement that provided favorable credit terms for the Soviets.

Against a backdrop of worsening American-French relations, the ministry spokesman expressed "distress" that a U.S. official claiming to be responsible should hide behind the anonymity of a background briefing to make "inexact allegations."

Far from being secret, the spokesman said, France had concluded a "financial agreement" with the Soviet Union in 1980 and fully informed the Organization for Economic Cooperation and Development.

The 24-nation OECD acts as a kind of registry and clearinghouse for member countries' credit policies with the Soviet Bloc.

State Department spokesman Dean Fischer said Friday the French "have informed us and other allies of the most important terms contained in this agreement, but they have not provided us copies of it."

The Pentagon charges provided conservative former president Valery Giscard d'Estaing with a rare opportunity to agree with the present, Socialist-led government.

Giscard called the charges "fanciful and irresponsible."

Analysts here noted the charge came from the Defense Department--rather than the State Department, as might have been expected. They said that the Pentagon had led the fight against soft credit for the Soviet Bloc.