The U.S. attorney's office here denied today allegations that one of its prosecutors orchestrated the fabrication and alteration of documents in a criminal case, contending instead that she ordered only minimal revisions to enhance the accuracy of the documents.

"Mistaken though that action may have been, it was not an obstruction of justice or any other form of deliberate misconduct," the court papers said.

In an angry response to the allegations made by attorneys for Omni International Corp., a Rockville-based jet airplane trading company indicted in a multimillion-dollar tax fraud case, the U.S. attorney's office said the Omni lawyers had turned a routine pretrial motion into a "series of personal attacks" on the prosecutor, Assistant U.S. Attorney Elizabeth H. Trimble, and on IRS agents Donald Temple and Paul Mitchell.

Throughout the 144-page response signed by Trimble, U.S. Attorney J. Frederick Motz and another assistant prosecutor, John G. Douglass, the office maintained that its procedures in interviewing potential witnesses against Omni and preparing memos of those interviews were proper and acceptable in federal court.

"Paradoxically," they said, "the techniques employed by Omni are frequently characterized as classic abuses of prosecutorial power: intimidation of witnesses . . . bullying trial tactics and disclosure of information to the press in a manner calculated to destroy the reputations of those whom they accuse." The court papers said that Omni attorneys had "broadcast" the allegations to lawyers not involved in the case and to "numerous officials in government" and, as well, "their personal attacks found their way to The Washington Post."

The Post first reported the Omni allegations on April 27.

Neither Motz nor attorneys for Omni would comment on the papers filed today.

The allegations and denials come as the government is preparing for trial against Omni, three of its corporate executives and its former attorney and accountant. The giant corporation is charged with siphoning millions of dollars in airplane sales and leasing income to an untaxed subsidiary in Bermuda. The defendants have denied all charges.

Last month, Omni attorneys filed a 700-page brief, claiming Trimble and IRS agents had altered or "created" at least 10 witness interview memos in a desperate effort to prevent dismissal of the case.

The attorneys said Trimble and the agents had unsuccessfully attempted to persuade former Omni attorney and accountant Joseph P. Bornstein to cooperate with the government by giving information about Omni's tax-filing practices in exchange for immunity from prosecution.

In an April 1984 motion to dismiss the case, Omni attorneys claimed that that effort, plus government interviews with other witnesses privy to information given to Omni by Bornstein, violated the attorney-client privilege of confidentiality.

Omni attorneys said that after Trimble was questioned by her bosses in the tax division of the Justice Department about possible weaknesses in the Omni case, she directed the IRS agents to alter existing interview memos or create new ones to reflect a heightened sensitivity by the agents in avoiding breaching the attorney-client privilege.

At an evidentiary hearing last summer before U.S. District Court Judge Walter E. Black Jr., a documents expert and other witnesses contradicted claims of IRS agents that several of the memos were written in 1983, prior to Omni's motion to dismiss. In fact, according to the testimony, the memos were prepared in the spring of 1984, most of them after Omni's motion to dismiss was filed on April 27, 1984.

In the government's response today, prosecutors acknowledged that the language of some memos was revised to improve their accuracy. "It is a common practice," the response said, " . . . that memoranda are drafted, edited and revised until, in the agent's view, they accurately reflect the substance of an interview."

In the Omni case, according to the court papers, "there were revisions to several memoranda which took place after Omni filed their motion. Mistaken though that action may have been, it was not an obstruction of justice or any other form of deliberate misconduct. Any changes were made in good faith to make the memoranda accurate."

In one case cited by Omni attorneys, IRS agents said in an original memo based on an interview with former Bornstein secretary Sandra Poe Wilkins that the contents of certain documents relating to Omni's overseas tax status "were not discussed due to the attorney-client privilege." That language was changed in a superseding memo prepared five months later, according to court papers, to say, "We told Wilkins that we did not want to discuss the contents of those memos due to the attorney-client privilege."

In their response today, the prosecutors acknowledged that Trimble had testified she believed the revised wording was prepared in late 1983 while an Omni expert witness said a 1984 watermark on the memo stationery and other evidence showed it was not prepared until May 1984, after the Omni motion to dismiss the case was filed.

Trimble's "forthright" acknowledgement of this indicates she is not "covering up" or committing perjury, as Omni contends, the prosecutors said.

As for violating the attorney-client privilege, the prosecutors contended that agents are free to ask potential witnesses any kind of questions, including those that violate the privilege. It is up to the witness, they said, to invoke the privilege. Omni attorneys had argued in other court papers that a pretrial ruling by federal Judge Joseph H. Young barred such questions.

Prosecutors also maintained today that minor inconsistencies in memos and the testimony of IRS agents are not part of a "massive cover-up," as claimed by Omni, but result from the massive paperwork generated by the five-year-long investigation into Omni activity. Agents "had only sketchy recollections of the dates particular memoranda were drafted," prosecutors said, "hardly a surprising event in a case involving contacts with over 100 witnesses and documents filling three rooms."