David Yassky may have been auditioning for Congress the other day at a City Council hearing.

Seconds before a committee was set to vote on the mayor’s 20-year trash plan Wednesday, the Brooklyn lawmaker who is running for a congressional seat, did something that would be commonplace in the House of Representatives but is virtually unheard of in the largely scripted council: He tried to attach an amendment to the plan.

While lawmakers have always been allowed to introduce last-minute amendments, the council has historically spurned the practice in favor of a culture of consensus. With the backing of Speaker Christine Quinn, the body earlier this year passed rule changes aimed at freeing up lawmakers to offer amendments, but none had tried to substantively alter a bill on the fly until Mr. Yassky did so.

The move did not catch the committee completely by surprise — Mr. Yassky made his intentions known earlier in the day — but it did raise eyebrows in a chamber long devoid of parliamentary maneuvers.

It also failed, resoundingly. Not one of the eight other members of the Sanitation Committee voted for the amendment, which would have added stronger language and stricter mandates to a section of the plan requiring the administration to reduce the amount of trash that passes through certain districts in the Bronx, Brooklyn, and Queens.

Even Council Member Jessica Lappin of Manhattan, who opposed the overall plan, balked at Mr.Yassky’s proposal. “I find great fault with this plan, but I don’t believe this amendment makes it better, and I vote no,” she said at the hearing.

Mr. Yassky, a Democrat running in a tight House race in Brooklyn’s 11th district, said he expected that result. “It went over like a lead balloon,” he quipped yesterday in an interview.

(The amendment was not introduced during the full council meeting. Mr. Yassky said he had intended to put it before a full vote, but decided not to because the meeting had run well into the evening.)

Mr. Yassky said he genuinely believed his amendment would have improved the trash plan, but fundamentally it signaled a protest against the legislative process. Although the mayor’s sweeping plan for disposing of the city’s garbage has gone through years of debate and several public hearings, council and administration officials hammered out its final draft in days of closed-door bargaining. Following tradition, Speaker Christine Quinn and her staff spearheaded the negotiations, with the expectation that the vast majority of council members would back the agreement that was ultimately reached. (The final vote was 44-5.)

That process, Mr. Yassky said, did not serve the council well. “There are a lot of important issues in that solid waste management plan that thoughtful people could differ on,” he said, adding that his amendment was not meant as a criticism of Ms. Quinn. “When all those important decisions are made in behind-the-scenes negotiations, you tend to wind up with public policy that’s less transparent and less good.”

To other members of the Sanitation Committee, however, the amendment threatened to rupture the fragile compromise that officials had reached after hours of painstaking talks. “We all felt that we had some victories and some disappointments in the final product, but for me, it was important that we put forth a plan that will be implemented,” the committee chairman, Michael McMahon, said. “If we all start to drop in unagreed-to amendments, then the thing would unravel.”

Although Mr. Yassky said he wanted to see the council function more like Congress, Mr. McMahon said city lawmakers had little choice but to build consensus. “The City Council is a legislative body, but our position in government is much weaker than that of Congress,” the chairman said.