FOR AN example of genuinely wretched legislation, there is the Senate Finance Committee's attempt to bail out the savings and loan associations. Everyone is Congress understands perfectly well that this device would work badly if at all. But the savings and loan industry, losing money heavily on the low interest rates of past years' mortgages, is pushing it with frantic energy. It's another loophole -- a tax-exempt savings certificate. The promoters have name it the All Savers amendment, and the Finance Committee has now voted it into the Reagan tax bill.

This new exemption would cost perhaps $3 billion a year. To the extent that it attracted new savers, most would go to the commercial banks since the banks will also be authorized to issue the certificates. To the extent that certificates are issued through the savings and loan associations, most will go to people whose money is already there.

The mathematics of the scheme makes it attractive only to people who are in the 32 percent tax bracket or higher. That means, for a typical family, an income upward of $32,000 -- the top one-fourth of all taxpayers. The All Savers amendment might better be named the Some Savers amendment. Like the basic Reagan tax bill onto which it is now being grafted, it sprays a great deal of money around, in the form of tax reductions mainly benefiting the more prosperous part of the population, with little attempt to focus its impact on its putative economic purposes.

The Finance Committee sees an urgent need to rescue the endangered savings and loan associations. Why? The traditional S&L is disappearing in any case. With the loosening of the federal regulation of financial institutions, the banks and the S&Ls are rapidly expanding into each others' businesses. And why should the housing industry get preferential access, through these expensive tax exemptions, to low-interest credit for its customers? What about the automobile dealers, or the appliance dealers, or all the other businesses that are unusually sensitive to interest rates?

The Reagan administration doesn't support the Some Savers amendment, but cravenly declines to oppose it. The Treasury does not want any arguments that might delay the bill. In its reckless haste to get the bill enacted, the administration is encouraging this kind of wasteful embellishment. eThe Reagan tax bill, originally to have been spare and simple, is rapidly turning into the most heavily decorated Christmas tree that you've seen in many a long summer.