Problem loans amount to nearly one-quarter of the National Consumer Cooperative Bank's $72 million loan portfolio, according to bank examiners. That compares with about 3.2 percent for the country's largest banks.

Problem, or nonperforming, loans are ones on which the borrower has ceased to pay interest or on which the maturity has been extended because the borrower is having difficulty paying.

The information about the Co-op Bank is based on an examination conducted last May by the Farm Credit Administration. It was released this week by Rep. Fernand St Germain, chairman of the House Banking Committee.

Congress established the National Consumers Co-op Bank to make loans to consumer cooperatives, with an initial government investment of $200 million. The bank is converting from a governmental to a shareholder-controlled institution.

St Germain said that this public investment is still whole, but he called for "decisive, quick remedial action" to restore the bank to a sound condition. Most of the bank's problem loans were made to housing co-ops that bought apartment complexes but ran into financial difficulties.

St Germain released the information on problem loans following disclosure by The Washington Post of an unusual letter to stockholders from the bank's chairman, Frank Sollars.

Sollars said in the letter that the examination revealed that 2 percent of its Title I loans, which amount to $62 million, and 27 percent of its Title II loans, amounting to $10 million, could result in losses. He said the losses were covered by reserves and therefore would not affect the bank's 1982 earnings. (Title I loans are made at market rates; Title II loans have softer terms for low-income co-ops.)

"While it had not been my plan to release the FCA report which is confidential , I think it now becomes important to place these numbers in the context of the overall tone of the report," St Germain said in a statement on the House floor Wednesday. "The number of classified loans was unacceptably high." (Classified loans are those regulators find to be problems.)

He further quoted from the report: "Although the poor quality of the bank's loan portfolio may have resulted partly from a business and lending philosophy deliberately formed with a greater tolerance for risk than was acceptable to conventinal lenders, the causes more easily discerned by the examiners were deficiencies in organization and in the capabilities and performance of credit staff."

Problem loans are increasing at all banks. Salomon Brothers' most recent survey notes that nonperforming loans as a percentage of total assets rose by 63 percent in the first nine months of 1982. The Office of the Comptroller of the Currency put the national average at 4.3 percent at the end of June.

Moreover, St Germain criticized the bank's disclosure policy on its management change. "For the past several months the bank has issued a number of limited and ambiguous statements concerning the status and plans for the chief executive office," he said. He urged the bank and the board of directors to make "an early and definitive public statement about the future plans for the most important position at the bank."

The bank announced in late October, following several weeks of rumors, that its president, Carol Greenwald, would take a three-month sabbatical. It declined to say whether she would be given a new contract as president when her current one expires at the end of January. Greenwald was offered an 18-month consulting contract. Mitchell Rofsky, executive vice president, was named acting president for the interim.