The Post has asked me to say a few words in defense of the Democratic Congress. As majority leader and sometimes spokesman for that heterogeneous and delightfully diverse collection of the people's representatives, I leap joyously to the task.

The Congress is not perfect. It is not an assortment of Olympian seers or as yet an assembly of saints. If it were, it would not be representative, and that is its function as well as its description. Congress is not easy to lead, or to speak for. Like the nation from which it springs, it is pluralistic and diverse, a distillate of the strengths and weaknesses, the virtues and faults of the electorate it serves.

Because it so seldom speaks with a single voice, the U.S. Congress makes a convenient target for the whole gamut of critics, comics and cynics who want someone or something to blame, who find scapegoats easier than solutions. Even members of Congress know they can always get a good press by roundly attacking this amorphous institution of which each of us is a part.

And so I swim against the tide when I report to you that this Congress, under the leadership of House Speaker Tip O'Neill and Senate Majority Leader Robert Byrd, has performed diligently, honorably for the most part, responsively to the public will and quite generally in the public interest.

Since January 1977, the Democratic Congress working both singly and with President Jimmy Carter has:

Lifted the country out of a serious recession, cut the unemployment rate appreciably and set in motion an unprecedented expansion of the private economic sector, with the result that nine million more Americans are gainfully employed today.

Supported a responsible international policy, including the strengthening of NATO and real increases in our military strength.

Voted two income-tax reductions, benefiting both business and individual taxpayers, in the aggregate amount of some $28 billion.

Reduced the annual budget deficit from a whopping $66 billion in 1976, President Ford's last year, to $29 billion in our last budget resolution and a projected $15 billion, which President Carter foresees for fiscal 1981. a

Made a genuine, if belated, beginning on the long, hard road to energy independence.

It is easy to find deficiencies. Congress has not, admittedly, eradicated all of the nation's problems. Critics who seek to fasten upon Congress opprobrium for all current ills are suggesting that we should double the nation's military expenditures, reduce everyone's taxes dramatically and bring the budget into absolute balance at the same time.

Those who share the responsibility of leadership do not have the luxury of promising glibly or teasing the public with unrealistic expectations. To do so would be a severe injustice.

It is an injustice, for example, to blame high prices on that old whipping boy, "big spending," and to suggest that inflation would magically end if Congress simply balanced the budget. As pointed out, Congress has been steadily lowering the annual deficit, not raising it. In one sense, a nation is like a family. How much it can afford to borrow is directly related to how much it makes. In this perspective, our position has improved.

The deficit for 1976 was 6 percent of our gross national product. The deficit is now only about 1 percent of current GNP.

Since Russia's invasion of Afghanistan, some of the very same people who've been excoriating Congress for big spending are now damning the legislative branch for having spent too little on defense. They'd have us believe that military expenditures have dwindled dangerously.

Well, the fact is that we spent $90 billion on defense in 1976, $130 billion this year. We'll budget about $158 billion for next year. Were it not for this increase -- which we consider prudent -- the budget would, in fact, be balanced.

America does have problems. The most serious are the energy shortage and persistent inflation.

The two are inseparably intertwined; they are, in fact, the same problem. The price of oil imports -- up 80 percent in just the past year -- is the principal cause of inflation. To think we can halt inflation without reducing oil imports would be to engage in the most dangerous form of self-deception.

The dollar drain for foreign oil has skyrocketed from $8 billion in 1974 to $60 billion last year. Were it not for our economy's dependence on ever more costly foreign oil, most economists agree, the inflation rate for 1979 would have been just about the same as for 1978.

To reverse the inflation rate, we have to reduce our dependence on imported oil substantially. That problem has been decades in developing. It won't be cured overnight. We promise no panacea.

But we have made some heartening progress. The nation used 8 percent less petroleum in November and December 1979 than it did in the last two months of 1978. Approximately 12 percent of America's families have fully insulated their homes. Our new cars are getting better mileage -- 21 miles to the gallon for the average 1980 model compared with 13 in 1974. Industry is using 16 percent less energy per unit of production than in 1974.

We still have a long way to go, but Congress and the nation are moving in the right direction.

Before this year is out, Congress will have approved 1) a dramatic synthetic fuels initiative, 2) a fast-track Energy Mobilization Board to cut red tape, 3) a comprehensive package of conservation incentives, 4) a solar energy bank, 5) a gasohol program, 6) new stimuli to exploration and recovery of more American oil, 7) utility plant conversions from scarce oil to abundant coal and 8) an Energy Security Fund of some $227 billion, from excess profits taxes, to help make America energy-independent by 1990.

Some criticism of Congress may well be justified, but not for want of effort. We make no claim to perfection. We just hope it can be said of us in the words of Harry Truman's favorite tombstone:

"Here lies Jack Williams. He done his damndest."