The Defense Department, trying to bolster its case in Congress for a new generation of chemical weapons, issued a new intelligence report yesterday asserting that the Soviet Union has stocked nerve gas at 32 Eastern European sites.

The report by the Defense Intelligence Agency cited a 26 percent increase in Soviet nerve gas depots since 1980 and warned that Moscow is researching new chemical agents capable of penetrating protective gear issued to U.S. troops.

Although the Reagan administration had persuaded Congress earlier this year to counter the Soviet threat with the first U.S. production of chemical weapons in 16 years, the House Appropriations Committee last week voted down a $164 million request to modernize the aging, obsolete U.S. stockpile.

A major battle on the controversial issue is expected when the appropriations bill comes up for consideration in the full House, possibly this week.

The administration argues that an obsolete and dangerous U.S. chemical arsenal leaves North Atlantic Treaty Organization troops in Europe unable to deter an attack by a Soviet inventory estimated to be 10 times larger. The average age of the U.S. munitions is 26 years, and Pentagon authorities say only 10 percent of the chemical arsenal is militarily usable.

"There is a fundamental problem," said Thomas J. Welch, deputy assistant defense secretary for chemical matters, who released the DIA report. "In short, the soldier and the sailor remain at risk. There is a Soviet threat, and that continues to build."

Congressional opponents who believe the U.S. inventory is sufficient to deter a Soviet attack in Europe said the report appeared to exaggerate Soviet strength in chemical weapons.

The report portrays a Soviet chemical juggernaut equipped with four kinds of lethal agents -- nerve, blister, blood and choking -- and an array of conventional weapons capable of launching them. One surface-to-surface tactical missile, known as Scud-B, can deliver 1,100 pounds of chemicals 180 miles, the document said.

A map of Europe displayed in the report shows 32 Soviet chemical weapons sites spread throughout the Warsaw Pact nations, with the heaviest concentration in East Germany and Czechoslovakia close to their common borders with West Germany.

Welch, who spoke at a Pentagon briefing, emphasized the safety benefits of the so-called binary chemical weapons that the administration wants built. Binaries consist of two chemicals that become lethal only after they are dropped by a bomber or fired in an artillery shell and mix together.

Current stocks of unitary weapons are lethal as they sit, and Welch said hundreds of munitions now stockpiled in eight states are leaking and should be destroyed.

He said the Pentagon spent $64 million last year monitoring the leaks and disposing of defective gas canisters. While they pose a "safety concern," he said, no one has been injured by leaks.