The Senate on Tuesday hastily passed an unpublicized amendment to the catchall spending bill that would apply its ethics rules to the House.

Under the change, House members would be prohibited from practicing law or other professions as members of firms. In addition, their names could not be used by such firms.

The change would also prevent House members from serving on boards of corporations, banking institutions or businesses except under special circumstances.

Under current House rules, members can be affiliated with law firms and have their names on letterheads. They are, however, restricted in the amount of income they can earn and the type of practice they and the firms can undertake.

The rules of both bodies permit members to practice professions as individuals with limits on earnings and types of cases that lawyers can handle.

House members were described as "surprised" by the Senate action, a key House Appropriations Committee aide said. "We're still trying to figure out what it means and what we're going to do about it," he added.

One congressional source said the Senate amendment may be tied to a piece of legislation that deals with handling changes in congressional pay. It, too, was attached without publicity to the continuing resolution.

This source said senators want the House to accept the pay measure and in return may drop the House ethics rule change. A Senate Appropriations Committee aide, however, denied there was any connection.

The pay provision would require that before a presidentially recommended pay increase could be killed, both the House and Senate, not just one chamber, would have to disapprove it. Now, the pay increase can be eliminated if one chamber votes against it. The Senate action, the aide said, was designed solely to conform handling of the pay recommendation with the recent Supreme Court ruling that barred one chamber, or legislative, vetoes. Three years ago, similar language was publicized as being attached to an omnibus spending bill with the result that the House defeated the entire measure.

The unusual Senate effort to change the ethics rules of the other body was offered by Sen. Joseph R. Biden Jr. (D-Del.). There was no debate.

Instead, Biden described his proposal in one sentence, saying it "applies to Senate and House rules with regard to participation in law firms and boards." That was all he said, other than it had been accepted by both the Republican and Democratic managers of the Senate bill.

It was then approved by voice vote, and the Senate went on to other matters.

The Biden amendment was not taken up in the miniconference on legislative matters last week but is expected to be discussed when the full conference meets Monday, a Senate aide said.

The measure would apply not only to members but to officers and employes of Congress who earn more than $25,000 per year.