The Government's major initiatives in antitrust enforcement may be meaningless without significant procedural reform, John H. Shenefield, assistant attorney general for antitrust, told Congress yesterday.

" . . . the ingenuity of counsel and the flexibility of existing rules of civil procedure have created a seeming inability to force major cases to decision," Shenefield complained in a hearing before the Senate Select Small Business Committee.

"Antitrust law, particularly in the monopolization area, can easily be subverted in favor of endless searches down back alleys for testimony that does not stand witness to anything, for mountains of documents that do not prove anything, and for lengthy briefs in support of legal theories that do not really mean anything," he said.

Shenefield noted that the division currently is attempting to focus, telescope, specific and narrow its largest cases, but he said changes in the procedural area - which he hopes will result from a recently established that not yet off-the-ground Presidential national review commission - are crucial. "Without procedural reforms, many of our substantive efforts may be for naught," he warned.

Shenefield said after the hearing he "shared monopoly" cases - will be meaningless "unless we can tell it to it's not too difficult to imagine what is worried that the division's proposed new initiatives - such as the planned "shared monopoly" cases - will be meaningless" unless we can tell it to the judge." Since the government's antitrust case against International Business Machines Copr. was nine years old week, with the trial still scheduled to run several more years, it's not too difficult to imagine what might happen should the government challenge several large companies on the same charges in one suit, he hinted.

Shenefield's testimony came during a hearing on the state of competition in the American economy and whether a broad review commission should be established. Shenefield has opposed such a commission but said he would support narrow focused studies on topics such as the impact of the tax laws or the impact of federal contracting policies on competition.

Shenefield also told the committee that he had named special assistant Douglas Colton to serve as a liason to small business. Colton's assignment is to expedite the complaints of small businessmen within the division.