A major piece of ethics legislation won the approval of a key House committee today after a group of rebellious freshmen delegates retreated from their threats to tack an amendment onto the bill that could have killed it.

The vote today came after a week long drama during which a veteran legislator had to be physically restrained from hitting a freshman delegate and other freshmen delegates traded insults with members of the House leadership, openly accusing them of sabotaging reform legislation.

Out of the conflict, however, came an ethics bill that would strengthen the conflict-of-interest and financial disclosure laws covering state officials in a state that has experienced a series of political scandals over the past 15 years.

The Senate has already given its approval to the ethics measure, but the House added some minor changes that require Senate concurrence. Some proponents of the bill indicated that the new version could face opposition when it returns to the Senate but remained optimistic about its ultimate success.

The ethics legislation seemed in considerable jeopardy earlier this week. House and Senate leaders who had carefully forged a broad coalition of support for the measure had not reckoned on a revolt by a group of angry freshman legislators.

What had piqued the newer legislators was the failure of a separate measure proposed by Del. Luiz Simmons (R-Montgomery), that would have put tight restrictions on a major source of political campaign contributions.

The bill, which passed out of the Constitutional and Administrative Law committee over the objections of its chairman, Del. Helen Koss (D-Montgomery), first won the approval of the full House and then went down to defeat the next day after another delegate successfully moved to reconsider the earlier vote.

The turnabout infuriated Simmons, who accused the House leadership of deliberately sabotaging a measure which, he said, was more stringent than the major ethics legislation that had the leadership's support.

In retaliation, a group of freshmen legislators-who hold 16 of the 22 seats on the committee chaired by Koss-devised a plan to amend the major ethics bill to inlcude the provisions in the defeated Simmons bill.

The power play alarmed the House leadership, which feared that, if the freshmen were successful, the delicately wrought coalition now supporting the major ethics measure would fall apart.

"I would have to go all the way around again and track all the bases, get to all the people who had worked on the bill... and get their concurrence" on the Simmons amendment," said Sen. John Carroll Byrnes, (D-Baltimore), the bill's sponsor.

"It is a major new concept in the election code... it would provoke a whole new debate." Byrnes said.

Additionally, with four days left in the session, it would have been virtually impossible to tack on any controversial amendments in the House committee, then have them debated and approved by both the House and the Senate.

On Wednesday, the Speaker of the House, Senate President James Clark (D-Howard), and members of the Senate committee which had considered the bill, paraded before the House committee to urge the delegates not to offer the Simmons amendment.

The freshmen bitterly resented the fact that the speaker and the Senate president had come before the committee to plead their case, and Del. Thomas Bromwell (D-Baltimore County) charged that the leadership was trying to "put on the last-minute squeeze."

By Wednesday night, tensions were running high. When Simmons ran into Del. Daniel Minnick, Jr. (D-Baltimore County) the speaker pro tem of the House, at a local bar, Minnick began chiding his younger colleague for going against the wishes of the leadership.

Later, outside the bar, according to Simmons and two other witnesses, Minick grabbed Simmons by the lapels of his jacket before he was restrained and escorted from the scene by a thrid delegate.

Then this morning, in an attempt to defuse the situation, Cardin summoned Simmons and the other freshmen members of the Constitutional and Administative Law Committee to his office and told them there had been "absoutely no leadership plot to kill" Simmons original bill.

Cardin then offered to cosponsor the legislation himself next year if it was modified slightly. Mollified, the freshmen agreed to give up their efforts to amend the major ethics bill, thus clearing the way for its approval. CAPTION: MAP, Map locates Minnesota Avenue station. By Dick Furno-The Washington Post