What could be controversial about legislation aimed at promoting the export of U.S.-made products, strongly supported by the Reagan administration and approved in the Senate by a vote of 93 to 0?

Quite a bit, it turned out when the measure was taken up in the House of Representatives. There, the bill known as the Export Trading Company Act of 1981--described by Commerce Secretary Malcolm Baldrige as "an important element in developing a coherent and comprehensive U.S. export policy to meet our international competition"--has encountered deep skepticism from senior committee chairmen, and its fate is in doubt.

The complex bill has aroused opposition because it would depart from half a century of banking and antitrust policy to encourage the formation of European-style export trading companies and allow commercial banks to own them. Export trading companies, well-established in Europe and Asia but little known here, are corporations that perform a variety of services, such as marketing, shipping, customs brokerage and insurance, on behalf of manufacturers--even competing manufacturers--who lack either the knowledge or the resources to do it themselves.

The Senate bill, supported by industry and banking groups, would extend antitrust immunity to such corporations and would permit commercial banks to own them, on the theory that the banks have the capital and the international network of contacts to make the companies effective in selling American products abroad.

Its supporters, led by Sens. John Danforth (R-Mo.) and John Heinz (R-Pa.) urged their senate colleagues to act swiftly and decisively on the bill last April because they anticipated problems on the House side, and their fears were well grounded.

Rep. Peter Rodino (D-N.J.), chairman of the House Judiciary Committee, balked at the antitrust provisions and offered a substitute measure taking a different approach. Rep. Fernand J. St Germain (D-R.I.), chairman of the committee on Banking, Finance and Urban Affairs, has expressed doubts about the wisdom of breaching the traditional gap between banking and trade in a move that critics say is not needed and won't work.

Both committees have jurisdiction over the bill. The Banking Committee is not expected to clear it until after Judiciary has completed action on the antitrust provisions, which could be before the end of the month.

The mechanics of export have traditionally been different in this country from what they are in Japan, Korea, Hong Kong and Europe. In Asia and Europe, much foreign commerce is channeled through what the Senate Banking Committee called "sophisticated, general-purpose trading companies which perform the full range of requisite functions for potential exporters." They manufacture nothing themselves, only arrange for export of goods made by others--often including competitive products made by rival manufacturers. Some of these firms are partly or wholly owned by banks.

In the United States, by contrast, a few large firms export their own products and most of the others ignore foreign markets entirely. According to the Senate report on the bill, "only 10 percent of the 250,000 manufacturing firms in the United States export. Fewer than one percent of these firms account for 80 percent of our exports."

A handful of export trading companies operate in the U.S. under a partial antitrust exemption granted in the Webb-Pomerene Act of 1918. The Senate found, however, that the exemption was so vaguely worded that the threat of antitrust action by the government discouraged the formation of trading companies.

The Senate bill would authorize the Commerce Department to issue certificates conferring immunity from government antitrust action on export trading companies dealing primarily in American-made goods. It would also authorize banks to own majority interests in trading companies, subject to the approval of bank regulatory agencies, on condition that they not grant more favorable credit terms to their clients than to others.

In the words of Sen. Paul Tsongas (D-Mass.), a strong proponent of the measure, "banks bring to bear their investment capital, international networks, and international financial expertise," making them the appropriate source of investment capital and management resources for export companies.

The key players on the House side of the Capitol, however, have refused to be stampeded by the Senate's overwhelming enthusiasm for the bill.

Rodino, citing reports by the Commerce Department and the U.S. Special Trade Representative, has argued that antitrust restrictions have a minimal impact on U.S. export trade. He and other members of his committee have also expressed reluctance to create a "new bureaucracy" in the Commerce department to issue antitrust immunity certificates , which they feel would be ineffective because Commerce approval would still not protect export companies against private antitrust suits.

Rep. Robert McClory (R.-Ill.), the judiciary committee's ranking Republican, and Rodino have submitted a substitute bill that would exclude export transactions from antitrust law altogether if they had no "direct, substantial and reasonably foreseeable effect" on domestic markets.

Rodino's committee approved the Rodino-McClory measure removing antitrust regulation from most export companies, but there is still sentiment within the business community and the administration favoring the creation of an immunity-certification process as well. A separate measure establishing a certification process is still under consideration.

The antitrust law section of the American Bar Association has argued strongly that an antitrust immunity certification process might actually deter the formation of the very export companies it is intended to encourage. In a report to Rodino, the antitrust section said small companies might balk at the time required to obtain immunity certificates and at the requirements to disclose proprietary information to the Commerce Department, and as a result might drop the idea altogether.

The Reagan administration has recommended that the barriers between commerce and banking that were set up in the Glass-Steagall act of 1933 be lowered. The banking and business communities have endorsed the bank-ownership provisions of the Export Trading Act, but St Germain remains unconvinced.

"He doesn't want to be the lone obstructionist on this," an aide said, "but there are problems over ending the banks' role as impartial arbiters of credit." One possible outcome, he said, would be a bill granting antitrust immunity but eliminating the bank ownership clauses.

As approved in the Senate, the bill would permit banks to hold minority interests in trading companies without the approval of bank regulators, but would require the approval of Federal bank regulators before taking a majority position or investing more than $10 million.

The regulatory agencies would be authorized to adopt regulations "designed to ensure against any unsafe or unsound practices that could adversely affect" the parent bank.