The nation's major banks have cut their prime lending rates by half a percentage point, following the Federal Reserve Board's recent efforts to ward off recession by bringing down the rates it charges banks to borrow money.

The new rate of 9.5 percent will ease the financial burden on some mortgage holders and others whose loans are tied to the prime rate, but economists said the half-point cut will not be enough to "jump start" an economy now officially acknowledged to be in recession."This is a step in the right direction," said Irwin Kellner, chief economist at Manufacturers Hanover Corp. "But neither lenders nor borrowers will rush to do business with each other on the basis of today's moves."

The prime rate is offered to banks' most credit-worthy commercial clients and is frequently the basis for setting home equity and other consumer lending rates.

It has not significantly changed since last January, when it was brought down to 10 percent from 10.5 percent.

Citibank, the nation's largest bank, and Morgan Guaranty, the fourth-largest, Wednesday followed the lead of San Francisco-based Bank of America Corp., the No. 3 U.S. bank, which lowered its rate Monday.

Manufacturers National Bank of Detroit, Pittsburgh National Bank, Continental Bank and NCNB Texas quickly followed.

They were followed by Chase Manhattan Corp., the nation's second-largest bank, and by Chemical Bank Corp., the sixth-largest U.S. bank.

First Union Corp., with banking operations in five southern states, also cut its prime rate, citing the Fed's actions and a "softening loan demand."

The new rates are effective immediately.

Kellner said he expected to see the prime rate fall another full percentage point to 8.5 percent by the middle of the year, following a decline in the federal funds rate to 6 percent and in the discount rate to 5.5 percent.

"I think the Fed will have to ease more in order to jump-start the economy. We're looking for the prime to go down one more point by the middle of the year," he said.

Another economist said the rate cut's effect will be small, partly because of the financial condition of the banks.

"I think the effect will be minimal because of the capital problems the banks have been having and the increased (government) scrutiny they are under," said Elliott Platt, director of economic research at Donaldson, Lufkin & Jenrette Securities Corp. in New York.

As a result, the banks will still be "reluctant lenders," he added.

Platt said the banks delayed following the lead of the Fed, which on Dec. 18 eased its discount rate half a percentage point to 6.5 percent, because of their need to boost battered profit margins by renewing some loans at the old, higher rates.

The cut in the discount rate, which banks charge each other for the short-term use of reserve funds and serves as a building block for other rates, was seen as an indication the Fed had acknowledged the nation's economy was deteriorating at a more rapid pace than previously thought.

Several medium-size banks responded to the discount rate cut, the most notable being First Chicago National Bank, which lowered its prime rate to 9.5 percent Dec. 20.

Depressed real estate markets, a current cause of many bad loans, are not likely to recover as a result of Wednesday's cut, Platt added, but are more likely to respond to changes in other financial instruments such as Treasury bills.

Other banks that cut their prime rate Wednesday included Marine Midland Bank of Buffalo, N.Y., the Bank of New York, Mellon Bank of Pittsburgh, Seafirst Bank of Seattle, First Federal Savings Bank of Boston, Harris Bank, a unit of the Bank of Montreal; Bank South of Atlanta and National City Bank of Cleveland.