NEW YORK, JULY 2 -- The courtroom revelation late last week of a Scotland Yard investigation into the origin of the Sevso Treasure has escalated the legal tug of war over ownership of the hoard of ancient Roman silver.

Sotheby's has touted it as "the most important late-antique silver ever to be offered publicly for sale." But according to an explosive report submitted June 28 to the New York Supreme Court by the Republic of Yugoslavia, one of the plaintiffs attempting to recover the silver, Scotland Yard is investigating three separate criminal offenses surrounding the complex antiquities deal.

The report alleges that "Such criminal offenses are all of the same gender, namely conspiracy to defraud, and arise because the silver was given false provenance in order to make it salable." The report says that all the parties involved, including Sotheby's and the solicitors acting for the seller, are subject to investigation.

"Scotland Yard has provided information alleging irregularities in the provenance of the Sevso Treasure," said a Sotheby's spokesman today. "Sotheby's has taken unprecedented steps, both in the degree of care and diligence used to publicize and disseminate information about the treasure, the purpose of which is to expose it to any possible claim. We strongly reject any allegation of misconduct and believe we have acted with the utmost integrity."

The silver was consigned for sale by the 44-year-old seventh Marquess of Northampton, through his family trust. The most spectacular allegation claims that Phillip Wilson, the son of the late Peter Wilson, former head of Sotheby's in London, went to Beirut in 1985 to obtain the fabricated export documents for the silver. Speculation in the London press has suggested that the late head of Sotheby's owned the silver prior to the marquess's acquisition in a long entangled trail of middlemen.

Halim Korban, a Lebanese antiquities dealer in London, was described in the report as part owner of the property when it surfaced there in the early 1980s and was also the agent for subsequent sales. In a telephone interview today from London, Korban said, "I cannot give you any information on the matter at the moment. This is an old story. If I'm at all involved, it's for the court to see."

Lebanon and Yugoslavia have joined forces, staking claims of patrimony over the extraordinary antiquities, reportedly discovered in a cave in Lebanon in the 1970s and miraculously preserved there in a huge copper caldron for about 1,400 years.

Lebanon and Yugoslavia, the plaintiffs in the suit, are challenging the $14 million bond they were ordered to pay by presiding Justice Carol E. Huff to freeze the sale. The figure represents 20 percent of the $70 million Sotheby's estimated the silver would fetch at auction. Lebanon and Yugoslavia would have to share the cash bond equally.

Sotheby's Swiss entity in Zurich planned to auction the incredible hoard in the fall. If no single buyer emerged for the 181-pound assembly during the expensive pre-auction world tour, the pieces would be sold individually in Zurich. But the controversy has vastly diminished the prospects of Sotheby's selling the consigned silver any time soon, if at all.

"Until the issue of who owns it and who has the power to convey true title is resolved," said Yugoslavia's attorney, Raymond B. Harding, in a telephone interview, "no one in their cotton-picking mind would pay $70 million for any treasure under these circumstances."

In 1984, the Getty Museum in Malibu was offered 10 of the silver pieces, but returned the objects convinced that the export documents were forgeries, according to the Scotland Yard report.

Back in February, Sotheby's New York mounted an unusual 10-day exhibition to promote the so-called Sevso Treasure, 14 huge and elaborately engraved and sculpted silver platters and vessels rich with hunting scenes from Greek and Roman mythology, dating from the 4th and 5th centuries A.D.

While Sotheby's publicized the treasures as being found in a cave in northern Lebanon, subsequent investigation, first reported in London's Independent newspaper by columnist Geraldine Norman, placed the discovery in a limestone cave on the Yugoslavian coast. It is speculated that elite troops of the late Marshal Tito found the silver and that a member of the Tito family smuggled the silver to London in diplomatic baggage, ultimately offering it for sale.

Throughout the New York court proceeding, Sotheby's claims the marquess had the necessary documentation for exporting the silver cache and had presented the licenses to the Lebanese Embassy in Bern, Switzerland, which examined and ratified the documents. But it has refused to relinquish these documents in court under routine discovery motions. In a court affidavit filed in February, Johnny Abdo, Lebanon's ambassador to Switzerland, stated, "... records of the Embassy do not contain any reference to any such filing about any property similar to the Sevso Treasure."