The House Commerce Committee yesterday adopted an amendment to telecommunications legislation that would ban American Telephone & Telegraph Co. from offering mass-media services.

By 25-to-5 vote, the committee easily approved the proposal by Rep. Timothy Wirth (D-Colo.) despite vigorous opposition by Bell System representatives. AT&T claimed the Wirth amendment would place severe restraints on the corporation's freedom of speech and had told some committee members that it had the votes to defeat the Wirth proposal.

The vote, which came early in a committee mark-up sesion on the controversial communications bill, was a clear victory for the American Newspaper Publishers Association, which had expressed concern that the legislation would have permitted AT&T, the nation's largest company, to expand its role in the delivery of news and advertising services.

Rep. Phil Gramm (D-Tex.), who bitterly criticized the Wirth amendment, said it was contradictory to the pro-competition themes espoused by the legislation's advocates.

Gramm said the newspaper industry was being treated differently than other communications concerns because "they have more clout than anybody else."

Wirth, however, said the issue in his amendment is a "much different issue than the ANPA vs. AT&T." Instead, Wirth said the question raised by his proposal is "who is going to control information and access to information in the electronic future?"

The legislation would deregulate many facets of the telephone industry over the next 10 years and would lift a 1956 consent decree between the government and AT&T barring the phone industruy giant from competing in unregulated markets.

In other action, the committee:

By a 22-to-5 vote, turned back a proposal by Rep. James Collins (R-Tex.) that would have removed from the bill a provision that allocated funds for interest groups intervening in communications regulatory proceedings. f

Defeated by a 29-to-11 vote a proposal by Rep. Andrew Maguire (D-N.J.e which would have prevented a new AT&T subsidiary, formed to compete in unregulated businesses, from using AT&T institutional symbols.

Unanimously approved an amendment by Rep. Lionel Van Deerlin (D-Calif.), chairman of the House communications subcommittee, that is designed to help avert a showdown over the bill with Rep. Peter Rodino (D-N.J.), chairman of the House Judiciary Committee. The amendment inserts the words "including structural relief" into a section of the bill that says the committee does not intend to affect decisions in antitrust cases.

Rodino has asked the Commerce Committee to defer action on key sections of the legislation dealing with AT&T restructuring until after the close of the government's antitrust case against the Bell System.

The referfral possibility was given further impetus yesterday when five other members of Rodino's monopolies subcommittee asked Rodino to seek a referral of the bill.