President Carter's once ambitious plans for a major overhaul of the federal bureaucracy are coming under increasingly skeptical questioning in the White House, where there is a clear decline in key aides' enthusiasm for the cause of government reorganization.

Carter came to office promising an upheaval in the structure of government and a reduction in the number of departments and agencies to 200. That goal was quietly abandoned long ago, and is now something of an embarrassment to White House officials, who concede that it was hopelessly naive.

There is no evidence that Carter is wavering in his devotion to the cause of reorganization, but the focus of the effort under way in the Office of Management and Budget has changed over the past two years, and is now hearing a crossroad.

A number of reorganization plans under development in OMB, among them a proposal to consolidate foreign assistance programs, may never be submitted to Congress, White House officials say.

Moreover, a sharp debate has developed over the fate of the two most ambitious plans to date, which would restructure programs in the areas of natural resources and community and economic development and, in one option, abolish the Commerce Department.

Some White House officials fear that a major reorganization drive could cost Carter political support in Congress and among interest groups whose agencies would be affected.

The most skeptical questions are coming from the domestic policy staff, under presidential aide Stuart E. Eizenstat, and Vice President Mondale and members of his staff, who are developing next year's legislative agenda.

Within OMB, where more than 300 people with a budget of $6.3 million are at work on the reorganization effort, the emphasis has shifted from structural changes to revisions of government processes, such as dfederal pay practices, cash management and data processing. One White House aide said, "You are going to see a lot more emphasis on waste and fraud in government, regulatory reform and that sort of thing."

But the reorganization team wants to make at least one big push, and they argue that it makes political sense to do so, despite the obstacles in Congress.

One aide said that in 1980 Carter will be called to account for his promises of 1976, and that, as things now stand, the president faces the prospect of going into the 1980 election having created two major government departments -- Energy and the proposed Education Department -- without eliminating any. Projects to improve the process of government, this person said, may be more important in the long run but have little political impact.

What Carter finally decides to do in natural resources and community and economic development will in large part determine the nature of the reorganization effort during the next two years. Recommendations have not yet gone to Carter, but the options being considered by OMB are sweeping.

Under one, for example, the Commerce Department would be abolished and its economic development functions transferred to a new community and economic development department modeled on an enlarged version of the Department of Housing and Urban Development.

But under another option, the Commerce Department would be expanded -- gaining some of the programs now administered by HUD -- and would become the focus of government efforts to foster foreign trade, absorbing the Export-Import Bank and the office of special trade representative.

Another option would create a natural resources department rendering the existing Interior Department "unrecognizable," according to one official, and would absorb in the new department agencies such as the Forest Service, now a part of the Agriculture Department.

But the sheer scope of these plans has some key presidential advisers jittery about the political costs involved and the impact that a series of bruising congressional battles over reorganization is likely to have on other administration proposals next year.

To buttress their case, officials who favor continued efforts to change the face of the federal bureaucracy hope to hitch their cause to the White House's anti-inflation crusade, the the president's top domestic priority for next year.

"If we move ahead with reorganization of the economic and community development system, the savings to the private sector and to state and local governments would be substantial enough to say it is part of the antiinflation effort," one administration official said. "If you reduce the manhours needed to handle all these development grant programs, in effect you provide more resources to use on other things."

The president's political advisers are not yet deeply involved in the debate, but they certainly will be before it is over. Most officials agree that the most radical of the OMB options -- abolishing the Commerce Department -- is not likely to be approved. But beyond that, few are willing to guess the outcome.

"I think there still has to be some element of structural change," one White House aide said. "I think we are vulnerable on that point."

Another presidential assistant with an eye on 1980 said he is waiting for OMB to convince him that the proposed major reorganizations would allow Carter to claim a significant savings for the government.

"Once you show me that, I could go for it," he said. "I want as a criterion the ability to say we saved so many millions of dollars by doing this."

The most significant proposal adopted yesterday by the Democrats took a small step toward cutting down on the number of subcommittees.

The proposal, offered by Burton, would limit the number of subcommittees a member could serve on to five. It would affect 84 Democrats who now serve on more than five. (Republicans, who make their own rules about serving on committees, would not be affected and have no such rule.)

A more stringent proposal, by Rep. John F. Seiberling (D-Ohio), to limit members to four subcommittees (affecting 120 Democrats) was rejected.

Proponents of both proposals argued that it was difficult for a member to give his or her attention to more than four or five subcommittees, and that there should be some "consolidating" of subcommittees. Exactly how subcommittees would be eliminated isn't clear, but Seiberling said he hoped the proposal would lead to a "trend in that direction."

The caucus adopted several leadership proposals to take care of what was a thorn in its side last session -- Republicans using roll-call votes to delay proceedings.

The changes will make it more difficult to get a roll-call vote on the floor, eliminate some procedural votes, cluster votes in certain cases and defer votes for a day in other instances.

One final change would affect the so-called suspension calendar. To ensure that the large flow of legislation from subcommittees would be taken up on the House floor, the leadership last session increasingly put bills on suspension, a procedure for speeding up consideration of legislation that allows no amendments but requires a two-thirds vote for passage.

The action led to complaints about abuse of the suspension process as bills costing $1 billion or more were passed without debate and without a chance for changes.

The caucus adopted a proposal by Rep. Allen E. Ertel (D-Pa.) that would not allow a bill costing more than $100 million to be brought up under suspension. Ertel's proposal also sets other "guidelines" for bringing bills up on suspension.

Today the caucus is expected to take up proposals on the rights of members found guilty of misconduct to chair subcommittees and vote on the floor.