The Securities and Exchange Commission yesterday ended a wide-ranging two-year investigation of the billionaire Hunt brothers of Texas by citing W. Herbert and Nelson Bunker Hunt for a minor disclosure violation.

The SEC accused the Hunts of failing to file reports disclosing they had acquired more than 5 percent of the stock of Bache Group Inc., the big Wall Street broker.

As usual in disclosure cases, the Hunts agreed to a consent judgment in which they promised not to violate SEC reporting regulations in the future, but neither admitted nor denied they had done so in the past.

The Hunts responded to the slap on the wrist by dropping a multimillion-dollar lawsuit they had filed against the SEC, accusing government investigators of violating federal privacy laws during their probe.

W. Herbert Hunt issued a statement calling the SEC case closed and saying he "continues to believe that our actions have been within both the letter and the spirit of the law at all times."

The settlement ended the SEC's investigation of possible securities law violations by the Hunts during the brothers' silver buying binge that ended in the spring of 1980 when the silver market collapsed. The Hunts had purchased hundreds of millions of ounces of silver over a six-year period, pushing the price of the metal from $5 an ounce to $50 an ounce before the bottom fell out of the market, costing the Hunts more than $1 billion.

While the SEC found no violations of its statutes except for the reporting omission, the agency said that by the end of the summer it will send Congress a staff report on the silver matter.

The SEC is expected to recommend changes in federal law aimed at preventing a recurrence of the incident that threatened some of the nation's biggest banks and brokers with financial disaster.

The Commodity Futures Trading Commission has been investigating the Hunts' silver buying for more than two years and a few weeks ago assigned additional staff members to its probe. The CFTC had once predicted its study would be completed by last January, but agency spokesmen now say they don't know when it will end.

The CFTC investigation is considered more important than the SEC probe, because the commodity agency has primary responsibility for regulating the silver market.

Limited to looking into possible violations of securities laws, the SEC subpoenaed tens of thousands of pages of documents detailing the Hunts' relationship with several of the nation's largest banks. The agency was trying to determine whether the banks violated the law by failing to tell their stockholders about the risks of their dealings with the Hunts, or whether the Hunts misled the banks about loans they obtained during the time they were buying silver.

Though the Hunts emerged all but unscathed from the long and costly SEC investigation, the family is still stuck with its vast and embarassingly low-priced horde of silver. Investigators say the Hunts' holding could still amount to 150 million ounces.

Silver prices have never recovered from the bursting of the silver price bubble in March of 1980, and the metal that once was worth $50 a ounce sold yesterday for only $6.53 an ounce.

The charges filed against the Hunts yesterday were based on information that had been public knowledge for more than two years. When the silver market collapsed, several banks and brokers disclosed that the Hunts and other customers owed them millions of dollars as a result of losses from silver futures.

At that time, Bache reported the Hunt brothers were not only major customers but also major shareholders, owning about 536,000 shares of Bache or 6.1 percent of the company as of January 1980.

Federal law requires anyone acquiring more than 5 percent of the stock of a public company to report that purchase to the SEC within 10 days. It was not until several months after their holdings became public knowledge that reports of the Hunt holdings were made officially to the SEC.

The complaint filed against the Hunts in U.S. District Court here yesterday spells out how Bache executives asked the Hunts to buy Bache stock to help the company fend off an unfriendly takeover by Canadian investors.