Individuals and society need not face increased risks of physical or social harm as a result of President Reagan's moves to cut the budgets of regulatory agencies, according to a report prepared for the Twentieth Century Fund.

If administrators reallocate their reduced resources and concentrate on the worst pollutors, for example, society may get the same level of benefit at a lower cost, according to Eugene Bardach and Robert A. Kagan, professors at the University of California at Berkeley.

But if administrators make a "uniform" cutback in their activities, Kagan said, "they may be endangering the public more than they have to. It is a people problem. What happens will vary from agency to agency."

Kagan and Bardach said that what has passed for regulatory reform in the Reagan administration so far has been little more than budget cutting.

"In general, the direction is right," said Bardach. "In some areas--like toxic substances and hazardous wastes--the administration has been too insensitive" to the dangers of decreased regulation, while in other areas that require changes in the law, the administration has not moved far enough.

For example, when the Clean Air Act came up for review in 1981, the administration made no attempt to change or force Congress to reexamine some of the provisions that, according to Bardach, impose a high cost on society with relatively little benefit.

Kagan and Bardach are authors of a new report, "Going by the Book," on whether regulators are "reasonable" in their enforcement of protective regulations, such as air and water pollution control, workplace and highway safety, and job discrimination.

To make regulation "fair, uniform, predictable and accountable," Kagan said, the laws often "impose a rigidity that deprives the regulators of the ability to adapt the rules to the variety of circumstances with which they must deal."

The report was funded by the Twentieth Century Fund and published by Temple University Press.

Often, Kagan said, regulations get passed to deal with specific catastrophes that are the "bad apples--the worst coal mines, the nursing homes that are the most avaricious." Because regulators often are deprived of discretion by the rules, they are unable to focus on the most serious threats and businesses are forced to divert their efforts to what the regulators say is the worst problem, not what businesses may judge to be the worst problem.

He said chances of cooperation between regulators and businesses are reduced because of these kinds of rigidities. Often, he said, the problem is not merely an overzealous or rule-bound regulator, but the difficulty in "determining what is a truly dangerous situation."

Bardach and Kagan said that most regulations have been written to deal with legitimate safety, health or social concerns that are "imperfectly dealt with by the marketplace and liability law."

In many, but not all circumstances, they say, the aims of regulation might be better achieved by more "indirect" regulation through private action. Self-regulation, which is practiced by many professional and trade associations (as well as stock exchanges), might be used in some circumstances. In addition, most harms have some remedy in the law, they said. Furthermore, to enable potential victims to take actions on their own, more information about potential hazards should be made public. The government, as a prod, might require wider disclosure.

Bardach said he and Kagan were surprised to discover that about 95 percent of the "regulation" in the United States is not mandated by government, but is done in the private sector.

While more regulation might be moved to the private sector, some has to be undertaken by government, they said; water and air pollution, for example, where the specific harms to individuals and the specific wrongdoings by polluters are hard to prove and measure, probably should continue to be regulated by government.

One of the primary reasons that government regulation is so difficult, Bardach said, is that the government "picks up the messiest regulatory jobs that no one can do well."