Five Washington-area credit unions, with a total membership of about 42,000 workers, have temporarily stopped making loans, and two others are now deciding each day whether to grant loans..

This further curtailment on loans, disclosed yesterday by area officials, marks the latest and most serious constriction in the availability of credit because of high interest rates. Those hurting the most are small- or medium-sized credit unions with smaller cash cushions.

The situation is expected to become more severe in the days ahead, with more credit unions shutting down their loan counters or restricting the amount of loans.

"There will be more (restrictions) before it is over," predicted Robert Von der Ohe, an economist who is chief of research for the Credit Union National Association, a trade organization.

About 2.6 million people belong to credit unions in the Washington area, with about $4 billion on deposit now, officials say.

Normally, credit unions offer their members comparatively low-priced loans to buy cars, make home improvements, finance vacations and consolidate bills. In addition, credit unions normally pay a higher rate of interest on savings accounts than banks or savings and loan association.

Loans have been discontinued at the crdit unions operated for employes of Giant Food, the U.S. Department of Transportation, the U.s.Office of Management and Budget, the Department of the Interior and The Washington Post.

There is only one exception to the no-loan policy. Credit unions are compelled by law to extend loans to members when the amount of money on deposit in an applicant's savings account exceeds the amount he wants to borrow.

At the credit unions for the Federal Deposit Employees and the National Labor Relations Board, officials consider loans on the basis of that day's cash flow.

"Some days we don't have enough to fill all the requests," said James W. Coyne, manager of the Federal Deposit credit union.

The nation's credit unions, including the 801 such institutions in the Washington area, have been forced to curb lending as depositors withdraw their money and place it instead in higher payming investments. Credit unions cannot pay more than 7 percent on regular accounts. But money market funds and some other certificates now pay 11 percent or more.

To counter the drain, some credit unions here have begun major efforts to attract new deposits.

In a newsletter to the 40,000 members of the credit union for Department of Defense workers, manager Robert E. Byroad asked them to consider "increasing your savings in the credit union . . . If every member would modestly increase his or her savings with us, the problem will be resolved and we can continue to give the kind of loan service that members want and deserve."

Credit union president Charles Steinecke III, in the same newsletter, suggested that they move funds from "an old-fashioned checking account which could cost you money" to a credit union account where it could earn 7 percent interest. The credit union account, he said, required no minimum balance, no service charge and no check costs.

As the pressure for credit has increased, credit unions have devised a variety of procedures to ration what money is available. The Fairfax School Employees Credit Union, for example, has a $500 ceiling on all loans.

The 2,000-member National Labor Relations Board credit union assigns a number to each application so that, as funds become available, loans are approved in the order in which they were requested.

The NLRB credit union also offers members small loans at rates of interest that exceed the standard 12 percent ceiling. On a $1,000 loan for one year, the plan provides for an annual percentagbe rate of 14.59 percent.

"The person would pay 12 percent on the $1,000 but he would get only $900 at first. After 12 months, when the loan is paid off, we refund the $100," said manager Joe Defrawi.

None of the NLRB credit union's members have applied for that loan yet, he said.

But John Thorner, an NLRB lawyer, did request and win approval for $3,500 home improvement financing from the credit union last month before the credit restrictions began.

The money was intended to pay for refinishing the basement of his brick home in McLean. "We just had twin girls, so we needed a bedroom fast," Thorner said.

He collected $1,500 from the credit union and contracted for the work. "But when I went back two weeks ago to get the money for the next payment, they said they didn't have any more money."

Thorner has other resources to cover the contractor's bill.

"But the irony is that I went down to the credit union that day for two reasons: To pick up the loan money to pay the contractor and to withdraw $1,000 from my savings account to buy into a money market fund."

The 2.6 million people who belong to credit unions in the Washington area are earning about $657,534 a day in a regular account paying 6 percent.

That works out to about 25 cents a day in interest earnings for one person.

If that same money were invested in a money market fund paying 12 percent, the interest would amount to about $1.3 million a day. The daily earnings for one person would be about 50 cents.

Actual interest varies, according to the institution and the method used to compute interest. Some credit unions, for instance, pay the full 7 percent allowed by the law and compound daily. And some money market funds pay only a little more than 10 percent.

But the difference has been enough to reduce the supply of money that normally would be in credit union accounts.

"We have a couple of options," said Miriam R. Soper, manager of the Department of Interior Federal Credit Union. "We can borrow money to meet our loan demand (from members), meaning we pay 14 to 16 percent to get money to loan out at 12 percent. Or we can decide not to make loans."

Interior decided not to make loans.