The White House said yesterday the success of President Carter's new anti-inflation program is "in doubt" because few business and labor leaders seem willing to make the sacrifices needed to slow wage and price increases.

During a briefing, White House press secretary Jody Powell complained that, while some companies and unions are cooperating, others seem reluctant to do as Carter has asked and settle for smaller increases than they got in 1976-77.

Powell particularly criticized those who he said are calling for Carter to impose tougher wage-price restraints, but who are unwilling to go along even with the present, relatively modest goals.

"The simple fact is that there are only two ways to go - voluntary measures and wage-and-price controls," he said. "Really, we've only got one way because wage and price controls have been shown not to work."

Meanwhile, Treasury Secretary W. Michael Blumenthal renewed the adminstration's opposition to a proposal in the House Ways and Means Committee to cut taxes on capital gains.

In a speech before a financial analysts' meeting, Blumenthal warned that, although new investment incentives almost certainly are needed, opening debate on that issue now only would jeopardize the president's tax cut plan.

"A detour into these structural issues can only endanger the broad consensus needed to enact the president's program," he said. "That is why the administration is strongly resisting . . . efforts to open up (these) issues."

Powell's comments appeared to reflect growing White House frustration with widespread criticism of the Carter anti-inflation program - specifically the charge often made by liberals that the plan is too weak.

The press secretary asserted that "it's wonderful to dream of some way . . . that is stronger than a voluntary program but is not wage and price controls," but said such talk is only "idle chatter" and is not realistic.

Meanwhile, Robert Strauss, the administration's new anti-inflation czar, assured a group of environmentalists yesterday the program would not seek to repeal present antipollution regulations, as some had feared earlier.

Strauss had cited the increased cost of meeting environmental regulations as factor contributing to inflation, and indicated he would look into it. The comments provoked a heated reaction from environmental groups.

But yesterday, the wage-price chief met with more than 40 environmental spokesmen and contended his previous statement had been taken out "of context." Sources said most participants seemed "pleased" by his remarks.

The administration recently has stepped up its anti-inflation "jawboning" effort, with officials pledging to use subpoena power if necessary to obtain wage-price information they need to monitor individual increases.

Powell made his remarks in response to a question concerning a recent poll that showed the public had relatively little confidence in the ability of the government to deal with inflation.

The tax provision Blumenthal attacked yesterday was introduced by Rep. William Steiger (R-Wis.) and is one of the major points of contention in the Ways and Means Committee's consideration of the Carter tax plan.