A deep rift within the Carter administration over proposed telecommunications legislation clearly surfaced yesterday as the chief of the Justice Department's Antitrust Division reiterated that Congress should not modify a 1956 consent decree between the government and American Telephone & Telegraph Co.

The Justice Department position, contained in testimony presented by Assistant Attorney General Sanford Livack to a House Judiciary subcommittee, comes just one week after Henry Geller, assistant Commerce secretary for communications and infromation, issued unqualified support for the vital section of the telecommunications bill now before Congress.

Litvack, reiterating previous Justice Department statements on the matter, said that "AT&T's monoply power should be confined to publicly regulated communications services" if the company's structure is not judicially altered. The Justice Department is seeking to break up the Bell System in its antitrust suit against AT&T, which is now set for trial early next year.ar.

"We have not been persuaded that there are facts or economic analyses sufficient to alter judgment or to require modification of the decree," Litvack said in prepared testimony.

Under questioning by members of the House Judiciary subcommittee on monopolies and commercial law, Litvack went one step further. "The decree was before a court, and I'd prefer that the court deal with such a decree," he said.

A week ago, Geller told the same panel that the bill now before the House lifts that decree -- which settled another government suit and barred AT&T from offering unregulated services such as data processing -- and permits the Bell Sytem to enter unregulated markets.

"We support provisions of H.R. 6121 [the Telecommunications Act of 1980] that deal with the decree," Geller told the subcommittee. "It is called for in light of marked changed in the communications field."

The subcommittee has been given a chance to review the bill until Oct. 1 because legislation, which passed the House Commerce Committee last month, deals directly with both the consent decree and the Justice Department suit.

Although criticizing the consent-decree sections of the legislation, Litvack said that, contrary to the view of some antitrust experts and AT&T competitors, the government's suit against AT&T should not be affected by the legislation.

The critics have charged that because the bill sets up a separate subsidiary for Bell unregulated operations, its enactment could bar the judge in the antitrust litigation from ordering AT&T to divest itself of key subsidaries.

Nevertheless, Attorney General Benjamin Civiletti, in an appearance last week before a consumer forum sponsored by Ralph Nader, noted that the Justice Department is "in a little bit of a bind or awkward position" about the legislation.

"Anything we say with regard to the legislation may be used in arguments against our position at the time of the trial," Civiletti said at the time.

Following Litvack, Charles Ferris, chairman of the Federal Communications Commission -- which in its so called "Computer II" decision began to address questions of Bell structure in unregulated business -- pointed out that FCC interpretations of the consent decree not the "ambiguities" of the decree itself.

Ferris said the FCC "does not yet know how effective" the establishment of the AT&T separate subsidiary will be in terms of opening up competition in the industry.

"In a nutshell, I do not believe that these relationships can be legislatively prescribed for all time in a single definitive legislative act without creating significant risks of anticompetitive practices or burdens on rate payers," Ferris said.