Sears, Roebuck and Co., the nation's biggest retailer, announced yesterday it plans to increase the minimum monthly payments on its 26 million charge accounts by about 25 percent.

A customer who now makes an $8-a month payment on a Sears account with a balance of $160 to $180 will have to pay $10 under the new rules.

Several other major leaders yesterday revealed plans to stop making consumer loans, curtail the issuing of new credit cards and take other steps to comply with the Federal Reserve Bord's edict to slow the growth of consumer borrowing.

But many lenders still are holding back on their plans, while they try to figure out how to limit credit without ignoring the rights of consumers or discouraging them from buying.

Sears officials said customers in some states may not have to make bigger payments, and residents of other states won't have to face them for as long as six months.

That's because laws in some states prohibit any changes in existing charge accounts, and others require lengthy advance warning to consumers.

The Federal Reserve Board staff is considering recommending suspending those state laws temporarily, so credit control measures can be put into effect immediately.

Federal Reserve governor Nancy Teeters is scheduled to testify about the Fed's credit control effort at a house consumer affairs subcommittee hearing today.

Two leaders of the Senate banking committee yesterday urged that lenders be prohibited from raising the monthly payments on existing charge accounts. It would be fairer to let consumers pay off old accounts at current rates, then raise the payments for future purchases, said Sen. William Proxmire (D-Wis.), chairman of the Senate Banking Committee and Paul E. Tsongas (D-Mass.), chairman of its consumer affairs subcommittee.

At least four states -- West Virginia, Iowa, Arizona and Maine -- prohibit lenders from raising the interest rates or payments on existing charge accounts.

Another 17 jurisdictions -- including the District of Columbia -- require that consumers be given advance notice of any changes.

Sears officials said the changes in their credit plan will go into effect as soon as consumers can be notified.

The giant retailer said it is not presently planning any restrictions on credit card use, but forecast changes in the way credit is granted for major purchases.

Sears officials said they expect more customers to buy major purchases, such as appliances, under separate time-payment plans that are exempt from the Federal Reserve's crack-down on credit.

In other efforts to curb consumer borrowing, Bank of Virginia yesterday disclosed it is taking steps similiar to those announced Monday by Citibank of New York.

The big Virginia banking company said it would no longer make new consumer loans to persons who are not already customers of the bank and will give new credit cards of overdraft checking accounts only to customers.

Bank of Virginia Vice President S. Joseph Ward said, however, there is no plan either to raise monthly payments or to reduce the credit lines for existing customers.

Maryland National Bank, the largest issuer of Mastercard in the Washington-Baltimore area, announced that it will cut off service to some 20,000 Mastercard customers who live outside the bank's service area and to some 909 customers whose accounts are severely delinquent.

Cardholders in the District of Columbia and states contiguous to Maryland will not be affected by the cut off of out of area cardholders, a bank spokesman said. He described the steps as "moderate" actions that will touch relatively few of the bank's 340,000 credit cardholders.

Union Trust Bancorp in Baltimore said it will begin monitoring delinquent credit accounts more closely and will impose limits on new credit to current customers.

New overdraft checking lines of credit will be limited to $1,500 and credit under Mastercard will be limited to $500. Personal unsecured debt for those who are already bank customers will be limited to $3,500.

During an informal House Small business subcommittee hearing yesterday five farmers and persons whose businesses are related to farming warned that the nation is nearing the crossroads where cheap food will end and higher food prices will begin.

The farmers complained that credit is so high that they are unable to make ends meet. An agricultural implement dealer from Greenburg, Kansas, and an oil jobber from Enfield, N.C. said that they are unable to extend any more credit to farmers and some farmers are going bankrupt, leaving them with thousands of dollars in debts they can't collect.

"We're going to see the same explosion in food prices as we've seen in energy prices," said Crawford Barber, an agriculture implement dealer from Greenberg, Kansas.