John F. Witte has a message for Congress: Do the tax-reform job, or admit you can't and pass the responsibility to somebody else.

Witte is a political scientist at the University of Wisconsin-Madison. In recent years, he has been studying tax legislation for a newly published book called "The Politics and Development of the Federal Income Tax."

In a paper he presented during last week's convention of the American Political Science Association here, he raised a troubling question, not just for his colleagues, but for the members of Congress returning to face the latest struggle over tax reform.

In essence, the question is this: Why is it that "the income-tax mess," as he calls it, has gotten worse since Congress reformed its structure and procedures in the 1970s?

Witte's argument is not easy to dismiss. He starts with the observation that the income-tax system is almost universally regarded as the "swamp of unfairness, complexity and inefficiency" that Henry J. Aaron and Harvey Galper called it in their recent Brookings Institution book, "Assessing Tax Reform."

Next, he makes the uncomfortable point that many of the worst features of the Internal Revenue code have been added since the House and Senate "democratized" their procedures in the 1970s.

Before that time, he points out, the inequities in the code were often blamed on the fact that the tax-writing committees (especially House Ways and Means) were special-interest bastions, operated largely in secret and controlled by powerful chairmen accountable to nobody.

So, in the 1970s, Congress "reformed" itself. It removed many of the Ways and Means Committee chairman's arbitrary powers, expaned the committee membership and made it more representative of the House, and ordered it to make its key decisions in public.

And what happened? Well, the evidence shows pretty clearly that after the procedural reforms, more loopholes and preferences went into the code, its complexity grew, and the revenue system failed by ever more massive margins to produce enough money to finance all the spending Congress was happily approving.

In short, Witte argues democratization and reform in Congress have taken a bad tax system and made it worse.

Is he right? Well, you can punch some holes in his argument. He does not note, for example, the one large area of congressional procedure which was left unreformed in the 1970s: the financing of congressional campaigns.

When Congress provided public financing of the presidential race, it left its own members to scrounge for funds from private contributors. Members of the tax-writing committees don't have to scrounge, of course. The contributions come rolling in to all of them who don't expressly forbid them, and some of those contributions clearly give the donors special access and influence when it's tax-writing time.

But I think Witte is right when he says that the basic problem goes deeper than that -- that it involves "a fundamental weakness of representative democracy." Deep down, most people prefer lower taxes and special benefits, as he says. And the "institutional arrangements" provided in the congressional reforms of the 1970s do "allow excessive, relatively unconstrained representation of short-term interests."

Well, if that's right, what's to be done about it? Witte's suggestion is to take the taxing power out of Congress' hands and give it to a "Federal Revenue Board," with members appointed by the president and confirmed by Congress.

He finds a parallel in the earlier decision by Congress to stop writing detailed tariff legislation on the floor of the House and Senate, where log- rolling produced such protectionist horrors as the Smoot-Hawley tariff on 20,000 named items, and to give the power to a semi-autonomous Tariff Commission.

The tax bill that Congress passed in 1981 in an orgy of generosity to every constituency "may not quite be Smoot-Hawley," he says, "but we are getting close."

I think his recommended solution is extreme -- and I'd like to think it's unnecessary. A Congress stripped of the power to set tax rates would be a sorry-looking excuse for the legislative branch the Founding Fathers wanted to make the foundation stone of the federal government.

The responsible actions taken by Congress in raising revenues in 1982 and 1984 demonstrate that it is capable of rising above itself and doing what the national interest requires. But those measures were not enough, and responsible action by Congress on taxes is now the only thing that will prove that radical remedies like Witte's are not necessary.

It's not just a revenue bill that is being tested. It's democracy itself.