Efforts by American Telephone and Telegraph Co. to force the Defense Department to release secret information from AT&T's competitors could threaten national security, government and private officials said yesterday.

Further, AT&T attempts to obtain the information in connection with discovery related to the Department of Justice antitrust suit brought against the giant telephone concern could also increase tenfold the cost of a $1 billion government research program, a government source said.

At issue is a series of documents submitted to the Defense Department in connection with its Independent Research and Development program. The documents, supplied under a confidentiality agreement with the government, offer significant planning, technological, and financial data about telecommunications companies that contact with the federal government.

"These companies are baring their technological souls," said a government source. "All the information is proprietary and some of it is top secret."

Ironically, AT&T, in challenging the government's suit which threatens to dramatically alter its structure, has cited national security as one of the reasons why the case is not in the national interest.

Nevertheless, AT&T, in connections with its massive discovery project across the federal government has gone to court to get the Defense Department files.

The Defense Department, a source said, spends about $1 billion a year in connection with the telecommunications program, and the costs of the program could jump to $10 billion if the government were forced to purchase the research reports from the companies after disclosure of the files to AT&T.

The issue is currently before U. S. District Judge Harold H. Greene, a federal magistrate and two special masters hired by the government to review facets of the antitrust case. The case is scheduled to go to trial in September 1980.

The materials are submitted to the government so it can evaluate the technology and also better evcaluate the finances of these companies when it is studying competitive contract bids.

The information includes secret technological plans dealing with such areas as laser use, fibers and satellitetechnology.

If it is forced to disclose the material, "the government will be unable to acquire the necessary scientific technology that it needs for the support of critical national security programs," the Defense Department said in a motion filed with the court.