Efforts to dismantle the Commerce Department in favor of a new trade department fell by the wayside last year in the crush of other government business, but the idea is still alive and kicking -- especially in the office of Commerce Secretary Malcolm Baldrige.

Baldrige has long supported a reorganization that would strip his large department of some of its eclectic responsibilities, which range from nose-counting at the Census Bureau to conducting marine research at the National Oceanic and Atmospheric Administration.

Under a Senate proposal drafted last year by Sen. William V. Roth Jr. (R-Del.), both Commerce and the Office of the U.S. Special Trade Representative would disappear, to be replaced by a new Department of International Trade and Industry with narrower trade-promotion duties. "A lean, mean, exporting machine" is how some Commerce officials have described it.

Even though the White House has never drafted a proposal, Roth's effort won wide endorsement in the administration, and Commerce officials expect the trade reorganization to get more attention from the top this year.

"It is a White House initiative," Baldrige aide B. Jay Cooper said yesterday. "The president spoke about it before he was inaugurated the first time."

The idea also got a boost recently from a presidential advisory panel. The Commission on Industrial Competitiveness, established last year to look for ways to boost entrepreneurial activity, last week endorsed a separate Cabinet-level trade department as a way to make international trade "a permanent national priority" and give the administration "a single, strong voice."

Whose voice that would be is still in question, raising the usual speculation about a power struggle between Baldrige and U.S. Trade Representative William E. Brock.

"That became an issue last year," Cooper said. "Baldrige said that if that was the only obstacle, he would resign."

For the nonce, Baldrige has no such plans. ON THE OTHER HAND . . .

Despite the obvious interest of the White House, at least one influential conservative group has come out foursquare against the idea of a new trade department. The Heritage Foundation, in its latest policy handbook, "Mandate for Leadership II," calls it an "unfortunate" idea that "would make the government far more susceptible to protectionist lobbying pressure."

Promoters of the idea contend that it would save money and help shrink the government by consolidating trade functions and eliminating duplication. The foundation ordinarily applauds that kind of argument.

"If the handling of international trade were turned over to one department, it would be far easier for industries to lobby for protection and costly subsidies for exports," the Heritage report warned.

If the department were established, however, the folks at Heritage leave little doubt as to which of the two current candidates they would prefer to see as its secretary.

Brock has been "fairly consistent in defending free trade," according to the report, while Baldrige "has been more receptive to protectionist arguments." AND BY THE WAY . . .

The Heritage report lists a number of other ideas for the second term at Commerce, including some that have been proposed repeatedly by the White House with a notable lack of success.

The foundation would like to abolish the Economic Development Administration, a "wasteful and unnecessary agency," along with the Minority Business Development Agency, the department's trade adjustment assistance programs and laws that restrict export of products banned in this country.

The report also suggests that President Reagan make tax reform a priority next year. However, in contrast to the plan proposed by Treasury Secretary Donald T. Regan, which generally would raise corporate taxes and eliminate a number of favored business tax breaks, the Heritage report calls for lower corporate taxes and more tax credits for business research.