The new leasing rules that Congress wrote into the tax code last year were much more than just a marketing system whereby businesses now can buy and sell tax breaks. They were a backdoor, largely unconsidered "reindustrialization" program for marginal and failing industries that will cost $27 billion by 1986.

Reindustrialization--a federal effort to help rebuild the nation's industrial base--has been a catchword and a subject of debate for some years now.

But the leasing program did not emerge out of a conscious public policy decision by the administration and Congress that the best way to provide support to the nation's beleaguered corporations would be to channel aid through the tax system and paper transactions called "leases."

Instead, tax leasing was almost an afterthought growing out of the realization that the 1981 business tax cut was so generous for profitable firms that it would place marginal companies--those whose profits were so low they owed little taxes in the first place--at a competitive disadvantage.

Now Congress is considering repealing or narrowing the controversial leasing provisions. But the interrelationship of leasing and the basic business tax cut means that a vote against leasing will be more complex than it seems on the surface:

"The business community has been a little bit asleep in thinking the debate over leasing is not going to spill over into ACRS," the new system of depreciation writeoffs for business that were the heart of last year's business tax cut, says Emil Sunley, former assistant treasury secretary for tax analysis and now tax analyst for Deloitte Haskins & Sells, a major accounting firm.

The leasing provisions have run into a number of political problems. The very idea of letting companies buy and sell tax breaks has offended some people. Others have been aroused by the fact that profitable as well as marginal companies have benefited from the liberalized leasing rules. Much less attention has been paid to the uneven effects of the basic tax cut that the leasing rules are designed in part to correct.

Last year's business tax cut was such that, for certain kinds of investments, the effective federal tax rate is now negative; the available tax forgiveness tends to be greater than the taxes owed on the income from that investment, which leaves the investor with extra tax breaks that can be applied to other income.

Or to put it another way, some kinds of investment generate not only normal income but an additional form of "income" through the tax code. Calculations by the Council of Economic Advisers, for example, show that, under the new law, a company buying construction machinery is likely to generate nearly one cent of "tax income" on every dollar of investment.

If it wants a 4 percent after-tax rate of return it need only make 3.1 percent in the normal way. By 1986, this subsidy will grow to 1.8 cents so that the pre-tax return on every dollar will only have to be 2.2 cents in order to get 4 cents after tax.

But for many of the nation's basic industries--automobiles, airlines, paper, steel and other metals--the business tax cuts are, without leasing or some similar mechanism, worse than useless. Healthy companies are helped; the unhealthy are left further behind.

But now as Congress, embarrassed at the fact that such profitable companies as General Electric and Occidental Petroleum are benefiting from the leasing rules, is moving to repeal or restrict tax sales, it is jumping past the equity issue: should the government help the weak?

Testifying to a generally hostile Senate Finance Committee, Frank Borman, president of Eastern Airlines, which has been planning to use tax leasing to finance $278 million out of $909 million to be spent for Boeing 757 aircraft, said:

"If you decide this leasing is too generous, then I suggest you decide that the accelerated cost recovery system ACRS and the investment tax credit are too generous.

"If you repeal tax leasing, you will have tilted the playing field enormously."

This tilt is also illustrated by the competitive situation facing Phelps Dodge, the nation's number two copper producer.

Phelps Dodge, like the rest of the recession-hit copper industry, is making no profits and pays no federal taxes. Without leasing or some other tax transfer mechanism, Phelps Dodge gets no investment tax credit or depreciation write-off on new plant and equipment because it has no taxable income against which to use these benefits.

In contrast, most of Phelps Dodge's major competitors, which together produce more than half the total copper tonnage annually, are owned by oil companies, including Kennecott by Standard Oil of Ohio; Anaconda by Atlantic Richfield; Cyprus Mines Corp. by Amoco; and Duval by Pennzoil.

While these copper companies are facing the same depressed market as Phelps Dodge, their parent companies are flush with profits and tax liabilities. These copper subsidiaries' tax breaks thus do have a value: they help cut the parent companies' tax bills.

For these subsidiary copper companies, even though they may be having net operating losses, the cost of new equipment is thus immediately reduced by 10 percent, the value of the investment tax credit, plus whatever the tax savings turn out to be from the new depreciation rules.

Some of the embarrassment created by leasing could have been avoided if Congress had been willing to own up directly to the implications of the business tax cut and make its benefits somehow "refundable."

If a company's tax benefits were greater than its liabilities, the Treasury would sent it a check for the difference. But this was deemed unacceptable by a Republican administration fearful of being charged with creating a form of "corporate welfare." Instead, the administration moved to achieve the same goal, but use profitable companies as intermediaries: firms like General Electric and IBM would "buy" the tax credits and depreciation write-offs from such marginal companies as Chrysler and International Harvester.

Just as would be the case with refundable benefits, the ultimate source of the money is the U.S. Treasury. But not all the benefit has gone to the weaker companies.

Of every revenue dollar lost, 22 cents has gone to profitable companies, and 2 cents to lawyers, investment bankers and other brokers, according to the preliminary findings of the Joint Committee on Taxation. (The Treasury does not dispute these findings, but contends the program is more efficient when a different type of analysis is used).

In other words, only 76 percent of the tax expenditure program is going to those who are supposed to benefit from the program. This compares, for example, to 90 cents of every food stamp dollar going to the intended beneficiaries.

In addition to only 76 percent of each dollar going to the target population of corporations, the law permits many highly profitable corporations--Occidental Petroleum and CSX, to name two--that already pay no federal tax because of other provisions in the code to sell their excess tax credits and depreciation write-offs.

By enacting a complex tax program with no restriction on the amount of tax breaks a profitable company can buy, the administration and Congress have allowed a situation in which one of the nation's largest profitable companies, General Electric, was able to get a net federal tax refund in 1981 of $90 million to $100 million.

GE paid cash to such firms as Chrysler and Phelps Dodge to gain this tax benefit, but nearly every participant in the controversy agrees that the ability of a company with pre-tax earnings of $2.66 billion to "zero out" its federal tax creates a problem, if only one of appearances.

A further problem is that the leasing rules were supposed mainly to benefit brand new firms and firms facing temporary losses. But in fact, the leasing rules turn out to be more beneficial to companies in chronically poor condition, or to profitable firms consistently able to reduce their federal tax liability to zero, than to the new company without any immediate profits or the firm facing temporary hardship.

This results from the fact that the new company and the temporarily profitless company, when they finally become successful, will have to start paying taxes on the money they make from their investments.

A brand new computer company, for example, might want to sell the tax breaks on new equipment because in its first year it has no taxable profits against which to use the credits and depreciation. If, in its second or third year, the computer company then makes a profit on the goods produced by the equipment, it will have to start paying a corporate income tax.

However, for a company that has sustained massive net operating losses and expects to be able to limp along for years using the losses to avoid federal tax, even well after it has gone into the black, the profits from new investments may never be taxable during the useful life of the equipment.

The effect is to create a distortion of investment decisions. The firm facing many years of no federal tax liability can afford to make investments producing lower profits than the firm that will soon shift into a situation where it must pay income taxes on its profits.

These problems are creating a minor revival among some members of Congress of last year's idea that the combination of relatively arbitrary depreciation schedules and the investment tax credit should be replaced with "expensing," a method of giving businesses an immediate first-year write-off of the full cost of the investment that is not subject to as much distortion.

There are other issues that were never considered when Congress adopted leasing. The basic question of whether it is a legitimate government policy to provide large amounts of aid to "sunset" industries is one.

A second is whether it might be more efficient to give some form of tax credit to persons who lose their jobs in failing industries, credits that could be redeemed by a company hiring the unemployed person. But in its rush now to stop embarrassing sales of tax breaks and to find new revenue to reduce forthcoming federal deficits, Congress seems unlikely to consider questions like these, much less the equity issues the leasing rules were meant to meet in the first place.