Washington area lenders again are raising the interest rates they charge on home mortgages and other loans and in some cases are turning away borrowers they would have accepted before.

In the past week mortgage interest rates have jumped a much as 7/8ths of a point. Mortgages are virtually impossible to find for less than 13 percent and many lenders are charging 14 percent or more.

Interest charges for overdraft checking and other consumer loans also are going up, although most Maryland and Virginia banks already are charging the maximum permitted by state law.

In those cases, many banks are refusing to make new loans, tightening their credit standards or restricting loans to established customers.

So far, bankers report, the staggering increases in the cost of borrowing show no sign of reducing consumers' reliance on credit.

Borrowers who quality for loans appear willing to pay the rates, the bankers say; only by refusing loan applications are the lenders able to cut down on borrowing.

Curtailing credit is the chief inflation-fighting strategy of the Federal Reserve Board, which last week raised the interest rate it charges to banks, triggering the latest round of increases in other interest rates.

"Mortgage rates are jumping all over," said Walter Preston, who publishes weekly reports on mortgage interest rates charged by local lenders. Preston predicted rates will go again next week.

Seven District of Columbia lenders and more than that in Virginia and Maryland already are charging 14 percent or more for mortgages, according to a similar service called Interest Data Reports.

Only two D.C. lenders were quoting rates below 11 percent and many lenders said they are marking mortgage commitments at "market rates," which are going up rapidly.

But few mortgage makers have closed their loan windows. "Availability is as good as it was at any time during 1979," Preston said.

Other lending is being cut back. Equitable Trust Co. of Baltimore, one of Maryland's biggest banks, has stopped making most consumer loans, senior vice president Bruce MacPherson said yesterday.

"We've been looking at the $99(Text ommitted) state Senate already has voted to lift gotten worse and worse," he said.

MacPherson blamed the curbs on consumer loans on the Maryland usury law, which limits the interest charges on most such loans to 12 percent.

Maryland banks are lobbying aggressively to change the law, and the state Senate already has voted to life the ceiling.

National Bank of Washington has raised the rate on Chextra, its overdraft checking plan to 15 percent, effective March 3. Customers who have outstanding balances can convert them to a 24-month installment loan to retain the 11.5 percent interest rate.

"We've had several customers that have converted to the installment loan at 11.5 percent, but they're still leaving their line of credit open, said Kenneth Tercero, senior vice president.

Interest rates on Riggs Line , Riggs National Bank's overdraft checking, will rise to 14 percent April 1.

Maryland banks have increased the rate they charge on loans under $3,500, but are limited to charging 12 percent on larger amounts of credit.

"It's an economic problem," said Warren Rothe, senior vice president of Suburban Trust. "It's very difficult to make 12 percent loans when you're paying in excess of that for the money to lend," he said.

"Marginal applications which may have been extended credit in the past may be turned down now," said Marge Muller, vice president for marketing at Union Trust of Maryland. Marginal cases where we feel there would be any difficulty in paying would not get the credit," she said. Some customers may get a smaller line of credit than they apply for.