The Carter administration has moved to prevent the New Hampshire utility company constructing the controversial Seabrook nuclear power plant from passing on millions of dollars in construction costs to consumers now, even though the project will not be completed for several years.

And there is no guarantee - because of environmental concerns and regulations - that any consumers, present or future, will derive any benefits from the plant. Construction has been halted by the federal government.

In a filing before the Federal Energy Regulatory Commission (FERC), the office of consumer affairs of the Department of Health, Education and Welfare has called on that agency to reject an appeal by the Public Service Co. of New Hampshire (PSNH) to pass along Seabrook construction costs "to meet severe financial difficulty."

The HEW office says that the utility's stockholders and investors should foot the bill for Seabrook instead of the consumers until, and if, the nuclear plant is complete and put into use.PSNH has spent $400 million and committed another $800 million to the plant, which is three years behind schedule.

Consumer advocate Ralph Nader bailed the filing. "This is a dynamite intervention," he said. "And it is the first time the White House has really moved on a consumer issue since Esther Peterson was given broadened powers." peterson has authority over the HEW office, and is exploring the possibility of moving into the White House and out of HEW. It was originally a White House office.

At stake in this Seabrook case is what as known as Construction Work in Progress (CWIP) and how it should be paid for. While the industry has long sought to charge customers for present costs, most utility regulatory bodies have sought to prevent the charging of consumers until they receive the benefits of the construction.

Some state utility commissions have, however, allowed certain CWIP costs to be passed on as they occur.

But state public utility commissions rule only on what costs can be passed on by utilities to their retail customers. The federal government has regulatory control over wholesale sales from one utility to another. PSNH has both types of customers.

In May the New Hampshire Public Utilities Commission allowed PSNH to pass along about $89 million it has already spent constructing the now halted Seabrook plant to its retail customers. According to PSNH spokesman Gordon McKenney, that $78 million represents about half of a 19 percent increase in utility costs to consumers in New Hampshire at the beginning of 1978.

But a decision by FERC on the subject is expected to carry considerable weight across the country, since most states use FERC decisions on accounting methods as a guideline for their public utility regulatory policies.

FERC rules allow CWIP costs to be passed on to consumers automatically in three situations:

When the utility has to spend money to meet pollution-control standards.

To aid in speeding up a switch from the use of petroleum to coal by a utility.

When the utility has an extreme financial hardship.

"It comes down to what type of financial shape PSNH is in," says FERC official John Alper.

So far, however, no utility has demonstrated the "extremely financial hardship" needed to pass on construction costs.

And in this case, according to the consumer affairs office, "a company [PSNH] which sets a five-year record high for its per-share earnings within a 12-month period during the last 12 months is "not under such financial distress to warrant the drastic relief for which it has petitioned."

"It's a question of current customers vs. future customers," said consumer office Director Lee Richardson in an interview. "How would you feel if you were retired, on a fixed income, and forced to pay a huge utility bill for a power plant that won't be operable for 10 years?" he asked. Such billing discrimates against today's consumers, he added.

PSNH spokesman McKenney confirmed the consumer office report that its earnings per share were at a five-year high at $2.94.But he said that figure was reached only because the utility was allowed to pass on Seabrook costs to its retail customers. Last year, he said, the earnings per-share figure was $2.17.

In its request before the FERC, the utility asks the agency to allow the utility to include Seabrook costs in its rate base, which is the total costs that can be used in setting rates.

"By allowing the CWIP into the rate base, it amounts to the customers paying the cost of money that is borrowed to build the generating facilities," McKenney said.

But Seabrook may never be constructed. Work on the plant was stopped earlier this month by the Nuclear Regulatory Commission until the Environmental Protection Agency can review the method by which water used at the plant would be cooled. The plant has been opposed by several environmental groups.