A bill to regulate the ethical conduct of public officials in scandal-tinged Maryland has run into serious trouble, jeopardized by rebellious freshmen members of a House committee who feel the measure may be too weak and vague.

The panel handling the ethics package -- the House Constitutional and Administrative Law Committee -- has shown signs of becoming a runaway committee as members in recent days have increasingly bucked the leadership of Chairman Helen Koss and House Majority Leader Donald L. Robertson, the principal architects of the legislation.

This trend imperils a bill, coveted by the speaker of the House, that would strengthen conflict-of-interest and financial disclosure laws covering state officials.

In addition, the rumblings of discontent on the panel represent a potential embarrassment for Koss and Robertson, two Montgomery County legislators elevated to leadership roles for the first time this year.

It was not a surprise that Koss and Robertson have had some trouble controlling this committee, stocked as it is with 16 freshman delegates, most without ties to the leadership or loyalty to the traditions of the legislature.

"That committee," said one veteran delegate, "is a rebellion waiting to happen."

The rebellion began this week.

On Tuesday afternoon, over the strenuous objections of Chairman Koss and Majority Leader Robertson, the committee overwhelmingly approved a measure that would prohibit corporations that do business with the state from contributing to political campaigns.

The bill was sponsored by Del. Luis Simmons, an energetic freshman from Montgomery County who spent three months researching the political connections of state businesses and presented such a well-documented case that 15 committee members ignored the leadership opposition and voted for his measure.

"Young Simmons was most impressive," said Del. Thomas B. Cumiskey, one of three veterans of the committee who voted for the bill. "After he presented his case, I said: 'Young Simmons, if I ever need a lawyer you're my man.'"

But Koss, Robertson and the committee's vice chairman, Del. Gerald J. Curran (D-Baltimore), were not so impressed.

Koss, visibly upset at the rebellion, chided the committee for making what she called "a serious mistake." Robertson told the committee that the measure may be unconstitutional. He cited a U.S. Supreme Court decision that he did not have in front of him and then went off seeking an advisory opinion from the attorney general's office.

Thereafter, Curran was dispatched to see if some committee members would reconsider the vote.

Curran discovered that most of the committee members were unwavering in their support of Simmons' bill and were not particularly concerned that their action might have embarrassed or angered the leadership.

"Curran talked to me after the vote," said Del. Donald J. Hughes (D-Baltimore County), "I kidded him by saying, 'Do you think we were bad boyd?'"

Del. American Joe Miedusiewski (D-Baltimore), a veteran who says he thinks with the independence of a freshman, said: "I think they were shocked that it got out like that. I guess we really pulled the rug right out from under them."

Although Koss and Robertson said they opposed the Simmons bill on its merits -- Robertson called it "a drastic bill" that "goes far too far" -- several members of the committee said they believed the leadership was motivated by an overriding concern for the ethics bill.

"I guess I walked into something that was a lot deeper than I realized," said Simmons. "I didn't put the bill in as an affront to anybody, but they seemed to be treating it that way. I can only surmise they feel it will conflict with their ethics bill."

As another freshman, Del. Michael J. Collins (D-Baltimore County) explained it, Koss and Robertson had another worry. They feared that, if they had to fight for Simmons' bill when it came before the House, they would risk alienating many delegates, and use up the political capital they needed to push their own ethics bill through the legislature.

"They may think that if they go to the floor with this reform measure, it will take too much time and possibly embarrass them to the detriment of the ethics bill," Collins said. "I can't believe that Helen and Don had an antireform motivation."

Robertson first presented the House version of the comprehensive ethics bill to the committee at a work session last Saturday.

After this session, many freshmen on the committee said they were disturbed by the leadership's approach to the bill. "Don and Helen made it very clear that they wanted to get the bill out soon," said one freshman, Del. David Bird (D-Prince George's). "It was like, 'here's the bill, now let's get it out.'"

Bird said that he and other freshmen on the committee began "digging through the bill line by line" at the Saturday work session and were not pleased with many parts of the lengthy measure. "It seemed to me that it was little more than a codification of the present law," said Bird. "In fact in some cases it appeared to be a weakening of the present law."

"There's a lot of sentiment on the committee not to let the bill out," said Miedusiewski. "It's just too ambiguous."

Cumiskey said he was thinking about the ethics bill as he drove home to Western Maryland after the Saturday work session. "I realize that the independent thinking group in the committee is sure not going to lie down on this one," he recalled. "They are going to want to know every detail of the bill before it goes out. I was driving along thinking, 'Boy, is this one in trouble.'"

The bill Cumiskey was referring to has been the subject of more than a year of work by Koss and Robertson, who are among the legislature's most persistent champions of reform. It also is a high priority of Speaker Benjamin L. Cardin, a liberal Democrat from Baltimore who hand-picked the two Montgomery delegates for leadership roles because of their reputations as progressives.

The measure drafted by Koss and Robertson is not the only ethics proposal in this general assembly session -- the Senate has already given preliminary approval to a lishgtly stricter measure. But proponents of the ethics legislation fear that traditional rivalries between the two chambers would make it unlikely for Koss's committee to approve the Senate measure if it had already rejected one that originated in the House.

Both bills gre out of a legislative effort in the 1978 election year session to reassure voters that public officials were serious about regulating their ethical behavior after years of scandal involving the state's top officials. Last year, an ethics bill passed the Senate but died on the House floor on the last night of the session.

This year's measures would set up a five-member ethics commission with the power to investigate allegations of corruption, issue subpoenas and enforce conflict of interest and financial disclosure laws. The new panel would replace a hodge-podge of boards and commissions that are without investigatory or enforcement powers.

Ironically, neither version of the ethics legislation has satisfied Common Cause, a reform-minded citizen lobby that for years has been pushing for enactment of an ethics law in Maryland.

"Although some provisions of each bill are worthy of public support, other provisions would actually weaken existing law," said Ed Riley, a Common Cause lobbyist. "We won't be disappointed if it doesn't pass. We would rather see no bill at all than one that is so full of holes."