The White House issued a report yesterday confirming what many critics have been saying for months - that President Carter's highly touted "zero-base budgeting" program has increased paperwork substantially without producing any dramatic cutback in spending.

In a 13-page "Assessment of the First Year of Zero-Base Budgeting," the White House said federal agencies "got off to a goood start" in putting the program into effect, but conceded the results were "quite subtle."

At the same time, the Office of Management and Budget announced it was modifying the program to try to cut excess paperwork and iron out procedural problems that some agencies encountered this past year. It promised "a smoother process and improved results" in fiscal 1980.

The document clearly was intended to serve as a plug for the ZBB program, which Carter put into effect last summer at the start of planning for the fiscal 1979 budget. The president had used the procedure when he was governor of Georgia, with similar results.

Zero-base budgeting differs from the traditional budget-making procedure in the agencies are required to offer top policy makers a choice of different spending priorities by showing what changes would be made if financing levels were increased or cut back for a program.

Those who used the program in Georgia have said the process increased paperwork substantially, but failed to produce significant savings or reallocation of resources - in part because many expenditures were prescribed by formal legislation, which could not be changed easily.

Yesterday's White House document reached much the same conclusion about the experiement at the federal level, arguing that ZBB "helped improve budget analysis" in most agencies, but cautioning that "neither ZBB nor any other . . . process can be substituted for . . . political . . . tradeoffs . . ."

The White House paper argued it was impossible to say precisely how much ZBB had saved the government because cutbacks generally stemmed from a combination of factors and savings often came more from not adding to current programs than from trimming them back.

Nevertheless, the document listed a dozen or so instances in which it claimed sayings were made as a result of the ZBB process. These ranged from elimination of 25 jobs from the Occupational Safety and Health Administration to phaseout of the Coast Guard's boating safety grant program.

James T. McIntyre, director of the Office of Management anad Budget, told a meeting of the Camber of commerce of the United States yesterday morning that the ZBB procedure had proved a "significant improvement" over the more traditional budget-making methods.

The procedural changes the administration is proposing for the program generally will relax requirements that agencies justify every dollar of the programs under their jurisdiction, and instead concentrate mostly on spending above so-called "minimum" levels.

The report yesterday conceded that many agencies "experienced difficulty" this past year in carrying out some of the new procedures. But it said much of the problem stemmed from the fact that the ZBB program was new.