Two new analyses of the Treasury Department's sweeping tax-reform proposal conclude that it would reduce investment, increase consumption and lead to no new gains in output.

Wharton Econometrics, a major national forecasting firm, said that, were the Treasury tax-reform proposal implemented, "After 10 years it would be a different economy," characterized by higher consumption, lower capital stock and a less competitive posture, according to Kurt Karl, Wharton's director of long-term service. "You would see more and more consumption of imported goods."

The National Association of Manufacturers said the Treasury plan was simpler for individual taxpayers and fairer than the current system. However, the plan also "ultimately would tend to depress long-run growth rates," said NAM Chief Economist Jerry Jasinowski.

The Treasury declined comment on the analyses until it has studied them, except to observe that some parts of the proposal were being disregarded in the studies.

The Treasury Department plans to release its own econometric study of its plan as soon as work on the federal budget is completed, the spokesman said.

Using an econometric model, Wharton found that the Treasury proposal would increase the cost of capital by 15 percent in 1986, rising rapidly to 20 percent on average for manufacturing industries after 10 years, Karl said.

For example, the user cost of capital for utilities would average 4 percent in 1986, rising to 9 percent; and for communications it would be 10 percent higher, rising to 15 percent. For primary metals, costs would rise from 15 to 20 percent, Karl said.

The increased cost of capital would be the result of the elimination of the Accelerated Cost Recovery System and the Investment Tax Credit. The reduction of the corporate tax rate from a maximum of 46 percent to a flat 33 percent would lower taxes for corporations in most cases and raise them in the others. The lower rates, however, would not offset the effects of the elimination of the special business tax breaks.

The Wharton analysis confirmed the revenue neutrality of the Treasury estimates, and after about 10 years there would be no real change in gross national product, Karl said. However, consumption would increase significantly because individual taxpayers would have more disposable income. Consumption would increase 1 percent by 1994, Karl said.

Meanwhile, business investment would be 4 percent lower by 1994, Karl said. In the short term, there would be little change in business investment.

The Wharton analysis was similar in some respects to that of another large forecasting firm, Data Resources Inc., which earlier said that economic growth would slow slightly, consumption would increase, investment would decline, interest rates would fall and inflation would not be changed appreciably.

Yesterday, at a breakfast meeting sponsored by the NAM, Data Resources' chief economist, Roger Brinner, said the DRI study also showed:

* The heavier corporate tax burden would lead to a 5 to 8 percent decline in the stock market.

* Lower interest rates would help reduce the federal deficit, "an effect which compounds substantially over time." The tax proposal would lower the deficit by about $70 billion each year by the first half of the 1990s.

* More generous shelters for retirement savings plans could help raise the personal saving rate.

* More people would be encouraged to join the labor force and work longer hours. More married women in low- and middle-income households would account for most of the labor force expansion.

The NAM preliminary study said the Treasury plan had many good points, but that it would increase the cost of capital, decrease corporate liquidity and lower capital investment. "This would ultimately translate into lower productivity and in all likelihood reduce economic growth," the NAM study said.

Small corporations would face a major increase in taxes. However, personal proprietorships and other corporations that are treated as individual rather than corporate taxpayers would benefit from the Treasury plan because the tax burden of individual taxpayers would decline compared to businesses, the NAM study said.

Using research of other economists, the NAM study said that "the alleged improvement in work and savings incentives for individuals" touted by the Treasury under its proposal "is more than offset by the increase in taxation on capital, with the result that such proposals must be viewed as more likely to depress the growth rate in the long run."

In addition, the higher cost of capital resulting from the elimination of certain business tax breaks, particularly ACRS under the Treasury plan, would reduce the international competitiveness of U.S. goods-producing firms, the study said.