The National Association of Manufacturers has called on U.S. business to live up to its "obligation" to increase plant and equipment investments in response to the tax incentives in President Reagan's economic program.

Alexander B. Trowbridge, president of the NAM, said the organization's directors approved a resolution calling on its 12,000 members to "move ahead with their investment decisions as quickly as possible," at a meeting last Friday.

The message followed some sharp criticism of the business and financial sectors by Treasury Secretary Donald Regan, who complained of a disappointing response to the president's tax program. "Where are the expansion plans?" Regan protested to a Midwest audience earlier this month. "It's like dropping a coin down a well--all I'm hearing is a hollow clink," he said.

Trowbridge said the 139 business leaders who attended the NAM board meeting last week believe Reagan's program will reduce inflation and help to lower interest rates over the next 12 months to 16 months.

He said he was optimistic as well that a significant increase in business investment would occur in that period, boosting employment and productivity in the economy.

But while the NAM polled its 139 board members about their general reaction to the Reagan program, it didn't ask the question on the Treasury secretary's mind: How many companies will make a significant increase in capital spending?

Jerry J. Jasinowski, NAM chief economist, said it is "unrealistic to think there would be a summertime splurge" in business investment following enactment of the business tax cuts. It takes more time than that for companies to review potential investments, in light of the new tax provisions, and decisions should not be expected until the fall, he said. The response will still come soon enough to improve economic activity in 1982, he predicted.

The NAM directors were considerably more confident about the impact of the Reagan program on inflation than they were about the outlook for interest rates. Of those responding to the NAM poll, 97 percent saw a reduction in inflation in the next year to 16 months, while 85 percent said the president's program would lower interest rates.

The business leaders weren't in unison on the course the Federal Reserve should follow in regulating the growth of the money supply. Some fear that the Fed's control may squeeze too tightly, causing a painful restriction of business activity. Others believe that continued tight monetary policy is necessary to continue progress against inflation.

"The issue was debated at length," Jasinowski said. There was a consensus that current Fed policy is "appropriate," provided that monetary growth remains within the range of 2 1/2 percent to 5 1/2 percent that has been tentatively adopted for next year by the Federal Reserve.

Trowbridge said the NAM directors also called on the group's membership to increase contributions to charitable organizations and other groups to help the administration's budget cuts in social services and other domestic programs.

President Reagan will ask business to make this voluntary effort, Trowbridge said, and the NAM directors will support him. But Trowbridge said he wanted to caution in advance against expecting too much from business. Corporations currently contribute 1.1 percent of pretax income to charities, he said, and while the new tax act raised the limits on deductible contributions, few companies will reach the new limit.