President Carter announced yesterday that a $10 billion fund has been created that will allow the savings and loan industry to invest in older neighborhoods that have been discriminated against in the past.

Carter said the fund is "just exactly what is needed in the extensive urban policy to reconstitute the vitality of our deteriorating neighborhoods in this country."

He said it is an example of the "new partnership" between private industry and federal and local governments that he had called for in announcing his urban program March 27.

The fund, which will operate for five years, was created by the Federal Home Loan Bank Board, the regulatory agency for the savings and loan industry, to increase urban investment by lending institutions.

The program is designed to permit the purchase and rehabilitation of at least 300,000 housing units.

Bank board Chairman Robert H. McKinney said the fund will not use tax dollars and will be aimed primarily at central cities although savings and loan associations in smaller communities may also participate.

As explained by bank board officials, the fund will work like this:

The bank system's 12 regional banks will borrow an average $2 billion a year for five years by issuing securities called consolidated obligations in the nation's capital markets. Such long-term securities now carry an interest rate of 8 to 9 percent.

The regional banks will then lend the money to savings and loan associations that present satisfactory plans for helping their communities. The regional banks will change the associations a rate at least one half of a percentage point below the current interest rate.

The district banks also will forgo certain service fees; so the local associations may save as much as three quarters of a percentage point on the special loans. They, in turn, will lend money at current market rates to community groups or individuals for construction or rehabilitation of low-income and moderate-income housing.

McKinney said the total cost of the program would be about $200 million, which equals the income of the system in one year, and he said the bank system will absorb the cost.

To qualify for the loans, local associations, which can borrow up to 5 percent of their savings from the new fund, must show that they plan to work with federal, state or local governments and community groups to "improve the attractiveness and availability of housing in older neighborhoods," said H. Robert Bartell Jr., president of the Federal home Loan Bank in Chicago.

Bank board officials said the program is not designed to overcome the tight money situation that the savings and loan industry now faces. The system already has a program of advancing money to associations to ease the money crunch. Under that program the system is expected to lend associations $8 billion to $10 billion this year.

Carter said the funds under the new program "will be a supplement to the normal monies available for lending now." He added that the funds would go to communities "that are badly in need of stimulation, revitalization, beautification, financial consultation, and the construction of low-and moderate-income housing."

The president noted that the bank board last month issued regulations prohibiting federally chartered savings and loan institutions from "redlining," or refusing to make loans on houses merely because they are old or located in inner cities.

He said he hopes the new $10 billion fund will lead to "more enlightened" loan policies.

Mayor Coleman Young of Detroit said the new program is a "very edible carrot . . . not only a lot of money but a program that we can plan ahead with." He said it would allow cities to attract more money from such federal programs as low-interest rehabilitation loans, urban development "action grants," and Economic Development Administration funds as well as private capital.

Several mayors attending Carter's announcement ceremony asked for assurances that the program would be geared to central cities.

McKinney replied, "The major thrust is going to be the central cities, but it's not solely for the central cities." Rep. Fernald J. St Germain (D-R.I.) added that areas outside central cities "have low-and moderate-income people with housing needs, too."