Treasury Secretary G. William Miller told retail bankers yesterday that "enormous" amounts of credit will be needed during this decade for energy development and productivity increases and, cnsequently, somewhat less will be available for consumer spending.

Addressing a conference on installment lending sponsored by the American Bankers Association, Miller said the Carter administration's fiscal policy is aimed at reducing the government's current high demand on the credit markets.

"We are at a crossroads," he declared. "It seemed for a while we would choose more government and more money thrown at our problems. Now the nation is saying very loudly that such a direction is not acceptable." Instead it is leaning in the direction of more free markets and the private enterprise system, Miller added.

While fighting high interest rates and strengthening the market system could only be good news to retail bankers, shifting the balance in the U.S. economy in favor of capital investment and against consumer could cut into bank's profits.

"This is the area that makes the money for the banks," declared ABA President C.C. Hope Jr. "Under no circumstances is the consumer credit industry going down the tubes. The American dream was built on being able to buy something now and pay for it later."

Hope's remarks preceded Miller's speech and therefore weren't meant as a direct response. However, they were typical of those made by many bankers who said that excess federal spending, not excess consumer credit, is responsible for today's inflation.

"Installment lending to consumer's far from being a balloon about to pop, is a solid and responsible part of our economy which will admirably bear the weight of these temporary restraints placed upon it (by the Federal Reserve)," said Hope.

Althought the ABA backs Carter's anti-inflation program, announced March 14, its members feel that credit controls were unnecessary because banks and sophisticated consumers already had begun to cut back. According to the the Federal Reserve, net consumer credit during the first two months of 1980 rose $4.2 billion, compared with a $6.5 billion increase during January and February 1979.

Robert B. Shanahan, executive vice president of Liberty National Bank & trust Co. of Buffalo, said one irony of the president's program is that it might cause a "credit card whiplash."

Pointing out that only 7.5 percent of total consumer debt is attributable to the use of credit cards, he added, "People who have never had one before

However, Shanahan, added, people won't stop using credit cards, which have become the universal form of financial indentification in this country. Check verification systems hae not proved as successful. Rather than return to checks as a form of immediate payment, more people either will use debit cards or use credit cards like checking accounts, payable at the end of the month, Shanahan predicts. More than half of credit card holders already repay almost at once.