Labor Secretary Ray Marshall, acknowledging uncertaintly over prospects for congressional approval of the administration's once highly touted "real wage insurance" proposal, asserted yesterday that the anti-inflation program can survive withoug it.

But he warned that the long-term success of any voluntary anti-inflation program requires a kind of "fairness" to workers tht the proposal attempts to achieve.

Apparently charting an escape route for use if Congress rejects the wage insurance idea, Marshall denied that the tax credit fir workers who abide by the administration's 7 percent guideline for wage increases is crucial to the immeciate fate of the whole program.

"I do not believe it is a linchpin or that the program would necessarily fall if we didn't have it," Marshall told reporters yesterday, putting on the record sentiments that Treasury Secretary W. Michael Blumenthal has also been voicing among his associates.

Congressional reaction to the idea, which President Carter displayed prominently in outlining his anti-inflation program last Octover, has been chilly. The proposal was included as an inducement to overcome organized labor's opposition to the wage guidelines. but unions, too, have been unenthusiastic.

The wage insurance plan, the only part of the anti-inflation program to require congressional approval, would provide a tax credit of up to 1 percent of a worker's first $20,000 in wages for each percentage point that inflation exceeds the guidelines -- up to a maximum of $600 if prices rise by 10 percent. At the current inflation rate of roughly 8 percent, the cost would be about $5 billion.

While saying that it was too early to be either optimistic or pessimistic about the proposal's prospects in Congress, Marshall said it could be important to long-range success of the voluntary anti-inflation fight "because experience worldwide has demonstrated that if it's not fair, it won't last long."