ROME, OCT. 13 -- The kidnaping of three Italian engineers by pro-Iranian Kurds today threatened to reopen Italian political debate over its naval presence in the Persian Gulf.

Prime Minister Giovanni Goria, who last month ordered an eight-ship naval flotilla to the gulf to protect Italian shipping, succeeded only last week in dampening opposition to the move by defending his actions before an often hostile parliament.

A new outcry erupted today after it was revealed late last night that Goria's government had kept secret the news that pro-Iranian Kurds are holding the three Italians in exchange for an Italian naval withdrawal from the gulf.

The Foreign Ministry and later Goria acknowledged the kidnapings after the National Union of Iraqi Kurds delivered a note yesterday to a news agency in Beirut. The embarrassed government said today it had been conducting "secret diplomacy" to try to get the three released.

Goria's office and that of Foreign Minister Giulio Andreotti, who is attending a conference in Bangkok, later disagreed about the timing of the abductions.

Aides to Goria said the three had been kidnaped five days ago. A Foreign Ministry statement said one had been held for a month, and that the other two disappeared two weeks ago.

{Engineering companies in the Milan area indicated Tuesday that they had learned of the abductions shortly after they took place, United Press International reported. One of those held, Giacomo Cominetti, 45, was seized Sept. 14 by four Kurdish guerrillas who invaded his working base near Mosul, in northern Iraq, his company said. The other two, Giuseppe Carrara, 32, and Roberto Diotallevi, 47, reportedly were kidnaped Oct. 2 from their work camp at Baiji, 60 miles north of Baghdad.}

Opposition groups, from the powerful Italian Communist Party to the neo-fascist National Movement, today accused the government of bad faith in suppressing news of the abductions during last week's parliamentary debate.

Goria's opponents argued that the Kurds' demand for an Italian pullout from the gulf in exchange for freedom for the engineers should have been included in the debate.

Many legislators said today that the government should stand firm against the Kurdish demands, but communist parliamentary leaders called on the government for further explanation of its gulf policy a challenge Goria said he would answer in parliament Wednesday.

Others, such as Mario Campana of the independent left, demanded that Rome recall its three mine sweepers, three frigates and two support ships from the gulf immediately. The naval group successfully completed its first escort convoy in and out of the gulf on Sunday.

Like Britain, France and the Netherlands, Italy last summer turned down U.S. requests for naval support in the gulf, contending that a naval buildup would aggravate tensions in the vital waterway. But like the other nations, Italy joined the effort in August after western ships were damaged by Iranian mines.

"We are before a disagreeable ballet that one does not exaggerate to call tragic," the influential daily La Repubblica said today in a front page editorial castigating the government.