The Reagan administration, in its first worldwide human rights report to Congress, has downgraded economic and social rights while placing increased priority on criticizing political shortcomings of the Soviet Union and its allies.

At the same time, however, the 1,142-page report made public yesterday on Capitol Hill closely resembles in many respects the 1,140-page document on the same subject submitted by the Carter administration in its final days in office early last year.

The tone and language about friends of the United States has been softened in many cases, but the new report contains facts and analyses gleaned from U.S. embassies abroad that document extensive shortcomings of friends as well as foes.

The most clear-cut shift in the report covering 159 countries was the omission of economic and social rights on grounds that this concept "is easily abused by repressive governments" to justify political abuses.

The Carter administration had included "the right to the fulfillment of vital needs such as food, shelter, health care and education" among the internationally recognized human rights covered by its reports to Congress.

While eliminating those elements in its definition of "human rights," the Reagan administration report nevertheless includes sections on "economic and social circumstances" in the countries described "because of the moral imperative of conquering poverty and since an understanding of these circumstances is useful" in understanding the political scene.

In the initial weeks of the Reagan administration, when Secretary of State Alexander M. Haig Jr. announced that "international terrorism will take the place of human rights" as a priority concern and the controversial Ernest W. Lefever was named as the State Department's human rights chief, there was widespread expectation of a radical departure from previous policies.

The report made public yesterday, reflecting continuity as well as change, appears to bear the imprint of Elliott Abrams, the 34-year-old "neoconservative" who was picked last October to be assistant secretary of state for human rights. An internal State Department memo in connection with his nomination argued that human rights policy can be credible in attacking the Soviet Union only if it also addresses human rights violations of friendly nations.

Political strife in El Salvador, which is probably the most politically sensitive problem country for the Reagan administration at present, claimed at least 6,116 lives during 1981, according to U.S. Embassy data cited in the report. However, the study noted that some church sources claim the actual death toll among noncombatants is twice as much.

"Extreme leftist terrorists and guerrillas, right-wing death squads and some members of the government's internal security forces all had a hand in the violence," the report said. It did not assign shares of the violence to the left or right, saying that "in the vast majority" of killings it is virtually impossible to determine who is to blame.

The report claimed that "a downward trend in political violence" was noted in 1981. However, a new surge of killings was reported early this year with the approach of next month's scheduled elections.

Findings about other countries in the report include:

* Soviet Union. "Intolerance" to and "repression" of political dissidents grew worse in 1981, with about 10,000 dissidents believed to be imprisoned, exiled or undergoing forced labor. In all, some 4 million Soviet citizens are reported undergoing forced labor, half of them in prisons and labor camps.

* Poland. "Progress toward a freer and more open society ceased" with the imposition of martial law last Dec. 13.

* China. "A more prosperous and open society" since the death of Mao Tse-tung in 1976, but "significant limitations on individual rights and freedoms" remain.

* Taiwan. An "uneven" human rights situation was clouded in 1981 by "the mysterious death" of a Taiwan-born American resident, Prof. Chen Wen-cheng of Carnegie-Mellon University of Pittsburgh.

* South Korea. "Strong 'law and order' measures" of President Chun Too Hwan dominated the climate for political and civil rights.

* Israel and Israeli-occupied territories. The "complex human rights situation" in the occupied territories does not provide "all the human rights guarantees available within Israel itself."

* Egypt. Despite a tendency "to react with heightened sensitivity" to opposition criticism, government measures "remained within the bounds of constitutional and other legal safeguards" established there.

* Turkey. The martial-law government brought "a substantial improvement in one aspect" of human rights by stopping terrorism. Military commanders continue to exercise "wide-ranging powers" over press, trade unions and the right to assemble.

* South Africa. "1981 saw the continued existence of the apartheid system but also some movement toward modification of that system."

* Nicaragua. Civil and political liberties deteriorated in 1981. Some 4,500 political prisoners are being held.

* Guatamala. Politically motivated killings rose from 70 to 100 monthly in 1980 to 250 to 300 monthly in 1981. More are probably attributable to "the extreme right" or "government forces" rather than to "the extreme left."