The head of a New York State investigation of Gulf Oil Corp's participation in an alleged uranium price-fixing cartel has challenged the Justice Department's decision in the case.

In a May 24 letter to Attorney General Griffin B. Bell, the chief New York investigator, William F. Haddad, charged that the cartel continued to influence world uranium prices into 1975 - after the limits of a recent federal charge against Gulf.

The Justice Department charged Gulf earlier this month with a misdemeanor violation of federal antitrust price-fixing laws stemming from participation in the cartel. A department spokesman said then that a more serious felony charge was not filed because there was not sufficient evidence to show that conspiracy continued past Dec. 21, 1974.

That was the date the law changed, upgrading such violations from misdemeanors to felonies.

In his letter to Bell, Haddad said the department's explanations "are at sharp variance with information developed during the New York State Assembly's investigation . . ."

That information "which we shared with the grand jury, leaves no question that the cartel continued to influence world prices after that date," Haddad said.

He noted the Gulf continued to pay dues to the cartel and supplied documents showing that the payments were to be disguised.

Haddad asked what civil remedies were available and advised Bell that his office intended to petition the court for release of grand jury testimony, and to seek documents from the Justice and State Departments about contacts with the Canadian government, which Gulf claims directed the uranium pricing group.

Bell has acknowledged being contacted by Canada's attorney general about the Gulf case, but denied that political considerations played any role in its outcome.

Bell was out of the city and could not be reached for comment over the weekend. Associate Attorney General Michael J. Egan, who oversees anti-trust cases, said in a brief interview that the department simply didn't have the evidence to support a felony case. "You've got to show some effect on U.S. prices," he said.

The New York investigators held joint hearings on the cartel in Washington with the House Commerce subcommittee on oversight. Rep. John Moss (D-Calif.), chairman of the subcommittee, has declined comment on the Justice Department action.

The price of raw uranium - called "yellowcake" - used to make fuel for nuclear power plants rose from $6 a pound to $41 a pound in the early 1970s. Gulf said it participated in what it termed the "foreign uranium marketing arrangement" at the "express direction of the government of Canada."

Hadded noted in his letter to bell that the possible $50,000 for a misdemeanor conviction on the charge is less than the windfall profits on one ton of uranium.