Once again, Congress is "working itself up to a jobs program just at the wrong time" in "a waste of $5 billion . . . another signal for financial markets that Congress can't control federal spending," according to presidential economic adviser Martin Feldstein.

But that was 10 days ago, just as the congressional jobs-creating bandwagon was beginning to roll.

Now that it is racing at full speed, with congressional Republicans scrambling to keep pace with the Democrats, the Reagan administration is climbing aboard, too, with an offer of $4.3 billion in accelerated construction work and other forms of aid.

Yet for all the "jobs fair" atmosphere on Capitol Hill, even the Democrats' hoped-for $5 billion to $7 billion for jobs and recession relief would hardly nick the double-digit unemployment rate that the administration has forecast for the next year or more. A reduction of half a percentage point is probably the best that could be expected from the Democrats' program.

And most members of Congress know it.

Jobs legislation has become a kind of litmus test for compassion toward the country's least fortunate.

"Basically it is just symbolism because Congress won't spend enough--it can't spend enough--to make a real dent in the unemployment rate," Rep. Les Aspin (D-Wis.) said last week. "It's an attempt to show your heart is in the right place . . . to separate the sheep from the goats by showing where unemployment is in your priorities."

The problem is that, because of soaring deficits and widely shared fear about their economic impact, Congress is unable or unwilling to spend enough to "buy" a substantial reduction in unemployment, even if it could agree on whether it would be wise to do so.

Moreover, the stimulative effect of this kind of jobs creation is a matter of dispute.

As Feldstein indicated in his congressional testimony 10 days ago, there is debate about whether the spending, no matter how fast Congress tries to crank it out, will come too late in the recession-recovery cycle. Thus it might fuel inflation and prompt another application of brakes by the Federal Reserve Board.

As President Reagan himself put it in his annual economic report to Congress earlier this month, before he made his $4.3 billion jobs-and-relief offer:

"It is understandable that many well-meaning members of Congress have responded to the current high unemployment rate by proposing various public works and employment programs. However, I am convinced that such programs would only shift unemployment from one industry to another at the cost of increasing the federal budget deficit.

"Although programs to help the structurally unemployed are important, only a balanced and lasting recovery can achieve a substantial reduction in unemployment . . . . Only a healthy and growing economy can provide the more than 13 million jobs needed to achieve a progressively lower level of unemployment over the next five years."

Indeed, the economic impact of all of the jobs proposals would be far smaller than that of the 1983 and 1984 budgets. The tax cuts and spending increases in those budgets will add about $46 billion worth of jobs stimulus to the economy this year and $22 billion more next year, according to the Congressional Budget Office.

CBO came up with those figures, which dwarf the $5 billion or $10 billion jobs programs under discussion, by calculating what spending and revenues would be each year if the economy were operating constantly at 6 percent unemployment.

If unemployment had been that low in 1982, the budget deficit would have been $23 billion instead of $111 billion, CBO said. This so-called standard-employment, or high-employment, deficit is estimated to grow to $69 billion this year and $91 billion in 1984. Economists generally believe that year-to-year changes such as these, which do not include the budget impact of a recession or recovery, can serve as a guide to whether the budget will provide additional stimulus to the economy or tend to restrain it.

"According to CBO estimates, unless policies in place are changed, the standard-employment budget deficit will rise from $23 billion in fiscal year 1982 to $215 billion in fiscal year 1988," the agency said last week. "By this measure, fiscal policy would provide a near record dose of sustained stimulus in the 1984-1988 period."

The administration estimates the stimulus would be even greater because it shows spending, particularly for defense, rising faster than the figures used by the CBO.

But high-employment deficits are not the kind of thing members of Congress can easily point to back home. For the short run, there seems to be little else the Congress can do--or at least do as directly and simply--as spend what money it can to relieve suffering and provide jobs for a few hundred thousand of the millions of unemployed.

For the Democrats, jobs creation is an almost instinctive response dating to the New Deal, when it was widely applauded.

For Republicans, worried about the imagery of Reagan's economic priorities, including helping the rich by tax cuts while squeezing spending programs for those with lower incomes, it may be tempting fate to vote against jobs and soup kitchens. Republicans simply cannot be cast in the role of nay-sayers on this issue, House Minority Leader Robert H. Michel (R-Ill.) said he told the White House this month.

Even those who contend that jobs spending is more than just symbolism concede that anything that Congress is likely to do will hardly touch the basic problem of an unemployment rate expected to stay at historically high levels long after the predicted recovery gets under way.

"I don't think there's any argument that what we do will fall far short of meeting the needs of the country," said House Democratic Whip Thomas S. Foley (Wash.), who is coordinating the Democratic jobs legislation planning with Sen. Carl Levin (Mich.).

But "if we try to do everything, experience indicates we'll get nothing done," Foley added in explaining why Democratic leaders are shunning more ambitious proposals such as the AFL-CIO's $68.5 billion plan for jobs creation and humanitarian aid over the next year and a half.

It is not brash, younger Democrats pushing the leadership for bigger jobs program, but rather senior members such as House Education and Labor Committee Chairman Carl D. Perkins (D-Ky.) and Rep. Augustus F. Hawkins (D-Calif.), chairman of the employment opportunities subcommittee. Many of the new members are greatly skeptical about big, costly government programs and the distaste for deficits they spawn.

But even Hawkins, who with Perkins is sponsoring a $15 billion program that he says would employ 1 million of the long-term unemployed through late 1984, acknowledges the limits of federal jobs creation.

"Moving ahead with a jobs program won't solve the problem without economic recovery," he said in urging an overhaul of fiscal and monetary policy as well.