In Europe, where his firm monetarist convictions are associated with 1982's devastatingly high interest rates, under secretary of the Treasury Beryl Sprinkel is sometimes referred to as "Beryl the Peril." (His friends point out that the rhyming is wrong: "Beryl the Pearl" would come closer.)

But however pronounced, Beryl's name was mud around Treasury this week for what Treasury Secretary Donald T. Regan considered a free-wheeling indiscretion: While Regan was still in Washington, Sprinkel called a press conference in Paris last Sunday, at a meeting of major nations' finance ministers, without letting his boss know about it.

The press conference made page one last Monday in some newspapers: Unless the United States and its major partners cranked up an economic expansion, the international debt crisis would worsen, Sprinkel was quoted as saying.

"Beryl has tried to be good; he's really tried to discipline himself," sighed a Treasury colleague.

The irrepressible Sprinkel, a dogmatic monetarist, has very strong views on most economic issues, expresses them on the record and has often gotten out ahead of the secretary on sensitive policy matters. For example, within a few weeks after taking office in 1981, Sprinkel started to give Paul Volcker public advice on how to run the Fed and was reined in by Regan.

And at the end of the Versailles summit in Paris last June, Sprinkel almost derailed Regan's efforts to convince his European opposite numbers that Regan could keep an open mind on the value of intervention to stabilize currency relationships.

The net result of the most recent episode was an official "reprimand" from Regan to Sprinkel for giving the impression that the United States was shifting gears from an inflation-control policy to one giving priority to economic growth.

"They visited together," said a Treasury official, "and it won't happen again."

Since the Treasury says it still has no official transcript of the press conference (held under the aegis of the U.S. Information Agency) it is difficult to determine whether, in fact, Sprinkel signaled any change in American policy. "I'm not responsible for headlines," Sprinkel reportedly grumbled to a colleague.

Sprinkel's defense is that his press conference comments merely echoed his boss' congressional testimony on December 29. Regan had said: "What the United States, Europe and Japan can do to help promote credible growth in their domestic economies will be of major importance to each other and to the developing countries, whose current adjustment problems can be eased by an expansion of exports to the industrialized economies."

A front-page story in The New York Times from Paris on Jan. 17 quotes Sprinkel in language so parallel that he might have been reading from Regan's testimony. He was also careful, as the Financial Times said the same day, "to couch his comments in moderate tones. He made clear that he was not suggesting any massive relaxation of fiscal and monetary policies, which, he said, would lead only to more inflation."

Why, then, was Regan so upset? The Times, the Financial Times and some other reports suggested that the Reagan administration was doing an about-face. The Financial Times, for example, drew a contrast with the administration's more anxious attitude on the debt crisis since problems surfaced in Mexico. The implication was that the administration is knee-jerking to the problems of American bankers who need a bail-out.

Another clue comes from the Treasury official who said: "Regan wasn't pleased to learn about Beryl's press conference, which was organized at his Beryl's request, when he picked up the newspapers. The secretary is supposed to articulate policy."

Yesterday, after both Regan and IMF Managing Director Jacques deLarosiere flatly denied that an agitated deLarosiere had phoned Regan to alert him to Sprinkel's Paris statements, the tempest in the Treasury teapot seemed to be simmering down.

"We're all talking," said a Treasury source who was in the middle. "We're all friends."