American Telephone & Telegraph Co.'s top attorney told a House subcommittee yesterday that action on legislation revamping the Bell System should end any judicial efforts to restructure the company.

The testimony by Howard J. Trienens, AT & T's vice president and general counsel, was the company's clearest statement of its position in the legal debate about telecommunications legislation.

"A legislative determination of the future structure of the Bell System, such as that contained in HR 6121, should end the matter until Congress acts again." Trienens said.

"We do not believe it sensible or fair to expose the Bell System to double jeopardy by permitting the Deparmtent of Justice suit for divestiture to proceed," he said.

At the same time, however, Trienens noted that a section of the legislation barring the court from considering congressional action in determing relief in antitrust cases permits the Justice Department's suit to continue "with no restrictions on the determinations of liability or relief."

The remarks came during testimony before the House Judiciary subcommittee on monopolies and commercial law, which yesterday opened two days of hearings into the effects telecommunications legislation might have on competitive issues and the Justice Deparmtent's six-year-old antitrust suit against AT & T.

The Justice Department case, which was set for trial on Jan 15 by U.S. District Court Judge Harold Greene yesterday, seeks a massive breakup of AT & T subsidiaries.

The chairman of the subcommittee and full committee is Rep. Peter Rodino (D-N.J.). The subcommittee has been granted a referral of the telecommunications bill until Oct. 1. Rodino repeatedly has expressed concerns about the antitrust implications of the legislation, which easily passed the House Commerce Committee last month.

Trienen' testimony followed skeptical questioning of other supporters of the five-year-old legislative effort to rewrite the nation's communications laws. Supporters of the effort, including Reps. Lionel Van Deerlin (D-Calif.), chairman of the communications subcommittee; James Broyhill (R-N.C.); and Henry Geller, assistant secretary of Commerce, reiterated their view that a savings clause contained in the legislation prevents courts from considering the bill in deciding antitrust matters.

In his testimony, Geller stressed the urgency of the legislative effort, insisting that it is vital in solving the regulatory morass which has surrounded the merging of the telephone and computer industries.

Geller further defended both the language and intent of the legislation, and denied that Greene, in hearing the government suit, would be forced to consider the AT & T restructing dictated by the legislation.

"The short answer is that the court in the face of the express congressional direction to act ast the court sees fit upon the basis of the record in the case, will do so," Geller said.

The legislation would modify a 1956 consent decree between the government and AT & T and permit Bell to enter unregulated field such as the computer industry for the first time but would force Bell to conduct those efforts through a newly created subsidiary. AT & T already has announced plans to assemble such a new subsidiary, a program spelled out by a Federal Communications Commission decision that sets similar goals.

Although communications legislation is given a slim chance of passage by either the House or Senate this year, Rodino has committed himself to reporting the legislation out of his committee by the Oct. 1 date set by House Speaker Thomas P. (Tip) O'Neill.