The City Council speaker, Christine Quinn, is conferring with lawyers to see what action can be taken against a council member’s chief of staff, who made a death threat against another council member.

“We take death threats, threats of any form against council members and council employees, incredibly, incredibly seriously,” Ms. Quinn said. “We are researching what our legal options are, as a speaker and as an institution, to take action.”

Last week, after another council member, Leroy Comrie, abstained from supporting a measure to name a street after a black activist, Sonny Carson, Viola Plummer said: “If it takes an assassination,” he will not become president of Queens.

Ms. Quinn also condemned recent death threats against Ms. Plummer’s boss, Council Member Charles Barron, which were posted on an Internet message board popular with police officers. The authors of the threats are unknown.

“If they were made by an NYPD officer, they are even more outrageous,” she said.

The police department is investigating the matter.

Ms. Quinn said her director of security has offered Messrs. Comrie and Barron additional security protection and a security assessment of their offices. “In both cases, we have spoken to the highest levels of the police department,” she said.

In 2003, a political rival assassinated a council member, James Davis, at City Hall.

Ms. Quinn appears to be working to diffuse the racial firestorm that erupted at City Hall last week, when the council split largely along racial lines over the proposed Carson street name. The measure failed.

Mr. Comrie was expected to call for Ms. Plummer to be fired or censured by the council at yesterday’s meeting, but he remained silent on the matter. A City Hall source said Ms. Quinn had asked Mr. Comrie to abstain from speaking about Ms. Plummer at the meeting. He was “urged to cool off,” the source, who requested anonymity, said.

Ms. Plummer, who could be heard shouting above the din in Council Chambers during the contentious Carson vote last week, was quiet yesterday, seated near Mr. Barron in a floral skirt and straw hat.

A Web site tracking terrorist organizations that receives funding from the Department of Homeland Security says Ms. Plummer, 70, was a member of a now inactive black separatist group, the New Afrikan Freedom Fighters, in the 1980s.

Ms. Plummer said she had never heard of the organization.

“That’s absurd,” she said yesterday. “I am so tired of making newspapers sell, you know, on the backs of people who are trying to change conditions for people of my race.”