Four years ago, the federal government borrowed a debt-relief plan from consumer credit agencies and began allowing thousands of former collegians to consolidate their various student loans into a single monthly payment.

In adopting the loan-consolidation program, Congress intended to ease the growing debt burden of students -- letting them stretch payments over longer periods -- in an effort to reduce defaults and associated costs to the U.S. Treasury.

A preliminary review by the General Accounting Office (GAO), mandated by 1986 amendments to the program, has found that borrowers may have received more financial relief than the government. GAO reported the program has increased federal loan subsidies and "may not significantly reduce defaults" on the federally guaranteed loans.

In the first two years of the program, more than 63,000 student loans totaling $905 million were consolidated by participating banks, credit unions and savings and loan associations. GAO auditors estimated federal subsidies of interest charges on those loans could cost the government at least $7.5 million more, in inflation-adjusted dollars. If the program grows as fast as the Education Department predicts, the amount of these subsidies could reach $365 million by 1994.

One cause of the additional costs, the GAO reported, was the extension of subsidies for as long as 25 years. Usually, the maximum repayment period is 10 years. Some consolidations also included types of loans that, though federally guaranteed, had not been government subsidized.

The auditors said only 107 borrowers defaulted out of the 63,226 who consolidated their loans through September 1988. But the agency said it could not estimate how many would have defaulted without consolidations or how many still might default. The GAO also said that borrowers who went through the trouble of consolidating their student loans had usually attended school for longer periods, making them less likely to default in the first place.

For borrowers, consolidations generally were found to have the benefit of reducing monthly payments. The reduction increased with the amount borrowed, ranging from 6 percent for loans totaling $7,500 to 31 percent for $45,000. Monthly payments on $10,000 in loans stretched over 15 years, for instance, would decrease from $121 to $101, a 16 percent drop.

But with their balances remaining higher for longer periods, borrowers also stood to pay more in interest charges. For the same example of $10,000 in loans stretched over 15 years, the total interest paid would rise by 67 percent, from $3,419 to $5,371 in inflation-adjusted dollars.

To be eligible to consolidate student loans, a borrower must owe at least $5,000 in loans and not be in default or 90 days delinquent on any of them. Covered are six types of loans, which have minimum monthly payments of $50 apiece and interest rates between 5 percent and 10.45 percent. Under consolidation, the interest rate is 9 percent or the average rate of the loans, whichever is higher.

With the program scheduled to expire in 1992, GAO recommended that Congress consider reducing its cost to the government by raising the interest rate, charging a refinancing fee, trimming interest subsidies to financial institutions or ending the student loan consolidations.