Portuguese Socialist Party leader Mario Soares has denied a statement attributed to him by The Washington Post last Friday that if elected prime minister he would hold talks with unions about denationalizing some government enterprises. In his interview Thursday with Post editors and writers Soares was asked whether he planned to "reverse the system of nationalizations in any specific sectors, to make changes in the land reform or the labor code" to resolve Portugal's economic problems. Soares replied, "I think so. I think it is necessary to do such changes in the labor policy, the code, but these changes have to be negotiated and agreed to with the trade unions." The Post editors thought his response applied to the entire question, including denationalizing industry, and regret any misinterpretation.

Portuguese Socialist Party leader Mario Soares said yesterday that a Socialist-led government would be in a favored position to carry out austerity measures needed for his nation's troubled economy because the powerful unions trust him more than the current conservative government.

Soares, whose party currently leads in polls forecasting results of national elections April 25, said that he would seek to enforce policies to boost labor productivity. The current Social Democratic-led government was unable to do that because of factional infighting with rightist coalition partners, the mistrust of the Communist-dominated unions and political opposition from the left.

"It is necessary to be able to talk to the workers and have them accept some sacrifices which are obvious," he said at a luncheon with Washington Post editors and reporters. "I think it is necessary to have a government that is trusted by the majority of the workers."

The center-right coalition government collapsed late last year and has assumed a caretaker status until the elections.

Soares, who was prime minister from 1976 to 1978, said he would hold talks with the unions on possible denationalization of enterprises. He said the country was in an economic crisis because of its $3.4 billion balance-of-payments deficit, 24 percent inflation and high unemployment.

Soares was in Washington for two days of talks with President Reagan and other senior administration officials as a representative of the Socialist International. He recently led a Socialist delegation that visited the Middle East, and he said he told Secretary of State George P. Shultz here that the United States should speed efforts to get Israeli forces out of southern Lebanon.

Reports from Lisbon suggest that Soares already has reached an understanding with the Social Democrats to form a coalition after the election. He said there was no formal agreement but acknowledged that "the idea is growing." Soares cannot seek a partner to his left because relations are practically nonexistent between his party and Portugal's pro-Soviet Communist Party.