Legislation designed to preserve independent newspapers in the United States will be introduced today by Rep. Morris K. Udall (D-Ariz.), who has warned of "disturbing social implications" from increased concentration of press ownership.

Udall has scheduled a Capitol Hill news conference this afternoon to urge congressional approval for a change in estate tax laws for the owners of current independent dailies or weeklies, "as an inducement not to sell their newspapers."

To qualify for the proposed estate tax relief, the newspapers could not be part of a chain (two or more newspaper publication) or publicly traded corporations.

In a series of articles on the nation's newspaper business in The Washington Post last summer, industry experts forecast that given current tax laws and economic conditions, a rapid concentration of press ownership is expected to continue.

Of about 1,760 U.S. dailies today, 170 companies own two or more and they account for 60 per cent of the total about 1,050 of U.S. daily circulation, the same 170 companies' papers account for 72 per cent.

"Because of the diminishing numbers of available independent local newspapers, chains have been buying other chains," Udall said. A major factor for the rise of chains has been "The devasting effect" of estate taxes upon owners of the independent papers, the Arizona Democrat added.

"More and more newspaper owners, in contemplation of the fact that their estates will not be able to both pay the estate taxes and maintain their newspapers, have opted to sell their newspapers in tax free exchange for the stock of chains and other publicly graded corporations," he said.

To ease this burden, Udall will propose "The Independent Local Newspaper Act," essentially an amendment to the Internal Revenue Code. The main provisions of the legislation include:

Permission for independent owners to established an advance estate tax payment trust, to be funded by corporate profits with not more than 50 per cent of pre-tax income of the newspaper in any one year.

Contributions to the trust and income would be invested in obligations of the federal government and excess funding would be prohibited: funds accumulated would be used only to pay estate taxes of newspaper owners.

Extension of the time for payment of estate tax where the estate includes interests in an independent local newspaper.

Udall said his approach would offer a "carrot" and "stick" approach to preserving diversified press ownership.

The funding of the proposed trusts would be from: pre-tax profits and the sums in the trust would not be part of the owner's estate for tax purposes , adding up to what the congressman termed "major tax benefits."

However, if owners of a paper with such a trust sell their publication, the bill provides penalties that would amount to 118 per cent of money in the trust, "to preclude an attempt to take advantage of this proposal."

Earlier this year, Udall introduced legislation to study economic concentration in major industries, including newspaper and book publisher. Similar legislation has been offered in the Senate and bearings on the proposed study by a competition review commission are expected in 1978.