In a prelude to the economic program he will announce today, President Reagan yesterday signed an order imposing strict new rules on regulators throughout the Cabinet departments and agencies, directing them to issue regulations only when essential and insisting that the least costly approach be followed.

The regulatory rules issued by Reagan create the lever that his administration intends to use to "get government off the back" of the American people -- and particularly off the back of business, which stands to benefit most from the adminstration's deregulation policies.

In separate actions yesterday, Reagan revoked the temperature control regulations established by President Carter to conserve energy and rescinded another executive order that would have sharply limited the export of hazardous products that are banned or restricted from use in the United States.

The temperature regulations, which were extended shortly before the Carter administration left office, required that thermostats be set no higher than 65 degrees in winter and no lower that 78 degrees in the summer. Reagan said that the energy conservative goals can be met adequately through voluntary action and that regulation is not needed.

In striking the restrictions on exports of hazardous products, Reagan directed the departments of State and Commerce to find ways to accomplish the same goals at a lower cost. The Carter administraion's order required exporters to obtain special licenses for products that had been labeled "extremely hazardous" after a review by government review by government regulators.

Vice President Bush, who heads the administration Task Force on Regulatory Relief, said yesterday's executive order creates the bureaucratic machinery "to make things happen. . . . There has been too much regulatory action which is adversely affecting our productivity in this country," Bush said.

"It's gone to an extreme, and we're seeking a balance," he added, promising that the administration would create more jobs by reducing regulation.

The order will have the greatest effect on the environmental Protection Agency, the Occupational Safety and Health Administration in the Labor Department and the National Highway Traffic Safety Administration in the Department of Transportation.

Not affected are independent agencies such as the Consumer Product Safety Commission and the Federal Trade Commission, although the administration has already moved to chang the thrust of these agencies through control over their budgets.

The order:

Requires executive branch agencies to identify "major rules" that have been issued or are under consideration, defining these as regulations likely to impose costs of $100 million on business or consumers or lead to "major increases" in consumer prices or industry costs.

Every major rule must be accompanied by a "Regulatory Impact Analysis" identifying the potential costs and benefits of the rule and a description of alternative approaches that could "achieve the same regulatory goal at lower cost."

Extends the 60-day regulatory freeze ordered by Reagan Jan. 29 by directing that major new rules that have been approved by executive branch agencies but have not taken effect must be postponed until the regulatory analysis is completed.

There are exceptions to this requirement that do not apply, for example, to regulations issued under a legislated or court-ordered timetable

Requires agencies to review existing major rules to pinpoint any that do not follow the least costly regulatory approach or duplicate other regulations.

The administration plans to rescind such regulations, new and old, aides said. Some proposed regulations can be changed dramatically by direct action, while a revision of existing ones would require agencies to reopen lengthy rule-making hearings, in many cases, aides said.

In general, Reagan's order directs regulators to issue no rule unless "the potential benefits to society from the regulation outweigh the potentail costs to society."

Regulators also are directed to set up priorities for action in order to achieve the maximum benefit for society, "taking into account the condition of the particular industsries affected by regulations" and "the condition of the national economy."

The language builds into government policy the concept that industry -- and thus society -- has only a limited amount of money to spend on regulations and that bureaucrats not only must find the least costly approach but must issue regulations that promise to achieve the greatest benefits, setting aside others that have a lesser impact.

The authority to monitor and enforce the new regulatory approach is given to the Regulatoy Task Force under Bush and to the Office of Management and Budget under its director, David A. Stockman.

Each can desiganate regulations as major rules, making them subject to the new requirements if agencies fail to do so.Each also can require agencies to consider more evidence and information in reaching final rule-making decisions.

OMB and the task force also are directed to work with Congress in proposing new legislation to reform the regulatory process.

According to Bush, the administration hopes to reach a consensus with members of Congress who have been pushing for regulatory change since the mid-1970s. Legislation is needed, he said to assure a change in direction for the independent agencies, but Reagan also intends to fill vacancies in these agencies with people who share the administration's determination to reduce regulation, Bush added.

Neither Bush nor his aides would identify a full list of major regulations they have in their sights, although several were mentioned by James C. Miller, executive director of the task force. He cited Department of Transporation rules that specify how transit agencies must make buses and subways accessible to the handicapped, and proposing EPA regulations governing noise