The United States' policy in El Salvador drew a barrage of criticism from congressional Democrats yesterday as the administration defended its record and asserted that the Salvadoran government has made "uneven progress" toward improving human rights practices.

"It should be clear to anyone who reads the newspapers that our side is not winning this war, that the political and economic situation is getting worse," said Rep. Michael D. Barnes (D-Md.), chairman of the subcommittee on Western Hemisphere affairs.

"Our current policy . . . makes a guerrilla victory almost inevitable," he added, calling on the administration to seek negotiations between the Salvadoran government and leftist rebels.

However, Thomas O. Enders, assistant secretary of state for inter-American affairs, while acknowledging that progress toward democracy has been "maddeningly slow," vigorously defended the administration's military aid to El Salvador as necessary "to hold off the insurgents and give time for economic and political reforms to go on."

He said more military assistance, in addition to the $26 million provided in the fiscal 1983 budget, "may well be needed" this year. The administration, he added, will ask Congress to transfer $35 million in economic aid from other accounts to supplement the $105 million El Salvador is expected to receive this year.

Hearings this week before the House and Senate opened a new round of what promises to be an increasingly acrimonious debate over policy in El Salvador, as the war between the government and guerrillas persists and the killing of civilians by security forces and insurgents alike continues.

Enders, testifying before Barnes' subcommittee, defended President Reagan's certification last month that the Salvadoran government has made progress in human rights, economic reforms, political democracy and national reconciliation. Such certification is required by law every 180 days for the administration to continue providing military aid to the beleaguered Central American nation.

Enders said the "land to the tiller" program, under which the Salvadoran government grants titles to peasant tenants, had been "vigorously relaunched" in the last six months. "During January alone, almost 27,000 additional acres were bought, based on 8,142 new title petitions from peasants working the land," he said.

Political violence is one-fourth the level of six months ago, Enders said, but added that Salvadorans accused of murdering American citizens have not been indicted because judges have been "intimidated or bought."

However, Rep. Gerry E. Studds (D-Mass.) and 80 co-sponsors introduced a bill yesterday to declare Reagan's certification "null and void" and suspend military aid.

"The Reagan administration has accepted a ludicrously low standard of performance in the area of human rights," Studds said.

Barnes echoed the criticism. "The certifications are made because they are necessary to keep the war going, and the administration has no policy except to keep the war going."

Although the administration had originally opposed the certification process, Enders hinted that it might support the law when it comes up for renewal this year.

"The leverage implied under certification has been helpful, indeed, perhaps essential," he said, and added, "How can you retain that leverage and eliminate the undesirable side effects, the fear of the consequences of a sudden cutoff?"

The Salvadoran military, he said, "failed to respond to the guerrillas' offensive in October and November as vigorously as they should have, thinking that supplies were not going to be replaced" because they believed reports that U.S. aid might be cut off.

Enders dismissed calls for the government to negotiate with the five guerrilla groups, which, he said, do not support a democratic government.

"Cessation of military aid would mean only that the fighting, now concentrated in four departments, would spread to all frontiers," Enders said.