A hazy-minded drug dealer who frequents New York's Studio 54 discotheque said in a televised broadcast last night that he once administered cocaine there to a man later identified to him as White House chief of staff Hamilton Jordan.

Speaking out publicly in the controversy for the first time, the dealer, John (Johnny C) Conaghan, acknowledged that he couldn't identify Jordan from photographs, since "I seen him only once," and gave the man cocaine only because he was with Studio 54 owner Steve Rubell.

Conaghan appeared on TV with Rubell and New York publicist Barry Landau, who said Jordan asked him for cocaine at the disco on the night in question. The program was a 20-minute segment of the American Broadcasting Co.'s "20/20."

Jordan declined to take part in the program, according to ABC, and White House press secretary Jody Powell was quoted as calling the airing of it "irresponsible."

The FBI is conducting a preliminary investigation of the accusations and similar charges that Jordan sniffed cocaine on a 1977 visit to the West Coast. The inquiry is being carried out under the new Ethics in Government Act to determine whether appointment of a special prosecutor is warranted.

Jordan has denied ever taking cocaine, and the White House has contended that his accusers in the Stdio 54 incident were making false charges in an effort to settle a $2.5 million tax-evasion case against Studio 54 and its owners.

Landau, described as "an inveterate namedropper," said Jordan singled him out on a June 27, 1978, visit to the club and asked him "where he could get some cocaine or coke."

Landau said, "I told him he was asking the wrong person," when Rubell walked up to be introduced to the White House aide.

Rubell, in turn, said someone -- he said he couldn't remember who -- told him, "Jordan would like a little coke," and at that, 'Johnny C.' was summoned. Landau said Jordan, Rubell and Conaghan then "disappeared for a while."

"He took a hit in each nostril," Rubell said of Jordan, insisting that he was telling the truth, even though admittedly plea-bargaining in the tax case.

Conaghan, who said he does "tend to get drunk" and who had had "a few shots of good old Russian vodka" that evening, said he "turned on two or three people" with cocaine, including himself. He said he was told several days later that the man with Rubell was Jordan.

"I put the spoon under his nose -- if it was Hamilton Jordan," Conaghan said.