Washington — The Reagan administration decision to sharply increase chemical warfare development in the United States is meeting with stiff public and political opposition.
A group of 40 religious leaders has organized a protest, and five denominational presidents recently came to Capitol Hill to voice their opposition. Legislation to ban increased spending for chemical weapons is gaining congressional support, and judging by extremely close votes on the issue last year, the Reagan administration's plan to produce chemical shells and bombs for the first time in more than a decade may be blocked.
The debate reflects sharply different perceptions about preparing for chemical warfare. The Pentagon contends that because of clear Soviet superiority in chemical weaponry, the US needs to boost its capabilities as a deterrence. Neither side used chemical weapons in World War II, it is argued, because both sides were well equipped.
Opponents acknowledge that the Soviet military is far ahead of the US in this area, but say American and allied forces have sufficient deterrent and retaliatory strength without resorting to chemical weapons. Europeans especially worry that most victims of a chemical exchange would not be soldiers (who are issued defensive equipment) but unprotected civilians. Two-thousand scientists in Britain have signed a petition opposing chemical warfare.
Underlying the debate is the increasing concern that the Soviet Union (in Afghanistan) or its surrogates (in Southeast Asia) may be using chemical weapons today. The Associated Press reported this week that a secret US intelligence report provides new ''hard evidence'' of such use.
Both the administration and its opponents seek progress in chemical arms control agreements with the Soviet Union, but officials here say the Soviets will remain ''intransigent'' unless the US has the clear ability and will to respond in kind to a chemical attack.
''If you look at their doctrine and look at the various exercises that they conduct, it becomes very obvious that not only do they plan to use it, they plan to use it just as they use conventional weapons,'' Army Maj. Gen. Niles J. Fulwyler warned in congressional testimony recently made public.
The Reagan defense budget boosts chemical warfare spending from $532 million this year to $705 million in 1983. This includes $30 million to produce new chemical weapons, which have not been built in the US since 1969. These are a 155-millimeter shell and the ''Bigeye'' bomb, both binary weapons in which two relatively harmless chemicals are mixed to produce deadly nerve gas.
''Although the principal thrust of these programs is to meet the threat posed by the Soviet Union, equipment is being developed to respond to a worldwide spectrum of contingencies,'' Defense Secretary Caspar W. Weinberger said in his annual defense posture statement to Congress.
''The US already has about 3 million . . . nerve-gas artillery shells and many other chemical weapons as well,'' says Art Kanegis of the Center for Defense Information. The Pentagon insists that many of these weapons are old and need to be replaced. The General Accounting Office has suggested the Army may be letting these weapons deteriorate to build its case for new binary weapons.
Senate Appropriations Committee chairman Mark O. Hatfield (R) of Oregon estimates the long-range buildup of chemical weaponry will cost as much as $6 billion. Disposing of the aging supply of existing toxic munitions over the next 15 to 20 years would cost $3 billion to $4 billion alone, according to the Pentagon.
Sen. Gary Hart (D) of Colorado, an Armed Services and Budget Committee member , has filed legislation halting funds ''for the production of lethal binary chemical munitions.''
The Senate last year fell two votes short of blocking a $20 million appropriation to upgrade the Army's munitions factory at Pine Bluff, Ark., where the binary weapons are to be built.
But lawmakers did include in spending bills the requirement that the administration provide more details on the chemical buildup, including a country-by-country report from the 15 NATO allies on how they view this change in US policy and program. Most allied governments are opposed to storing more chemical weapons on their soil.
In a recent letter to Secretary Weinberger, Mr. Hatfield said, ''I find it tragic indeed that we are unable to respond in ways more creative and consistent with our desire for moral leadership in the world, than to simply be imitative of Soviet behavior. . . . The NATO alliance should not be subject to another unnecessary and potentially divisive debate at a time when cohesion is of the essence.''