As a mostly black city and the seat of the federal government, Washington has seemed like just about the last place that needed a special committee to bring together federal agencies and minority business.

And Washington was just about the last place to get one. In 40 other cities there have been minority business opportunity committees - M-BOC - doing that job.

Washington's M-BOC got off the ground yesterday, with a little ceremony and a work session. Representing 16 federal agencies and the District government, the committee's job is to make good on President Carter's promise to triple government purchases of goods and services from minority firms.

As Undersecretary of Commerce Sidney Harmon pointed out yesterday, the government's purchases of goods and services from minority firms has increased dramatically in recent years.

In 1969 minority firms got only $220 million in government business. By 1977 that total was up past a billion dollars. By 1979 the goal is $3 billion plus. That's 15 times as much, Harman said, "That begins to sound like we mean business."

But last year all the minority firms in the country did only $30 billion of business, amounting to only 1.5 percent of America's $2 trillion economy. "That's inequitable, that is unsatisfactory and simply cannot be allowed to continue," added Harmon.

By 1982, he projected, the total output of minority firms will top $75 billion, in a $2.5 trillion economy, indicating the minority share of the market will be doubled.

"We're then finally beginning to talk seriously about a trend moving toward ultimate equity." said Harman, in his last public appearance before leaving government. Minority business efforts were a major assignment for Harman at Commerce, and the M-BOC committees are a key tool of that job.

The local committee will be run out of the offices of the Greater Washington Business Center, a minority business development and consulting firm financed by Commerce's Office of Minority Business Enterprise.

A major part of the job is old fashioned conscienciousness raising - impressing upon government agencies of their business to minority firms.Part of it is introducing minority firms to the prospects for government contracts.

Recent changes in the Small Business Administration law are supposed to increase opportunities for minority firms to tackle small jobs by requiring government contractors to give preference to disadvantaged small firms.

But the whole SBA program is in trouble, with Sen. Gaylord Nelson (D-Wisc.) warning that te'll try to abolish the agency unless it shapes up, and Nelson's Wisconsin colleague William Proxmire wanting to tear down SBA right now.

As the new Washington minority business group yesterday, Harman warned of "a rising tide of conservatism and determination to hold back his kind of program. The times ahead are not going to be easy times."