A veteran House member who earned a committee chairmanship under Speaker Salvatore DiMasi plans to vote against the House chieftain's bid for a third full term as speaker, and Monday became the first member of the chamber to discuss his decision publicly.

Rep. David Torrisi, House chair of the Committee on Labor and Workforce Development, told the News Service he would defect from DiMasi when the Democratic caucus votes next week on its leadership, citing the allegations of ethical wrongdoing that are dogging the speaker.

"I don't think this is going away," Torrisi said of the set of controversies. "I think this is a huge distraction for the membership."

Torrisi's decision, which he shared with DiMasi during a one-on-one meeting on Dec. 22, is the most formal signal yet of the membership's uneasiness about following DiMasi. The North Andover Democrat said he expects DiMasi to remove him from his chairmanship.

"I think that's pretty obvious," Torrisi said, laughing when asked whether he expected the removal. "I'd imagine I'd lose a staff member or two."

"It was difficult for me and I know he feels I let him down, but at the same time I think he's putting members in a very difficult, awkward situation come January 7," Torrisi said of DiMasi, who attended his wedding in 2006.

DiMasi has said he will seek another term, while some members have said privately they are uncomfortable lining up behind him while he battles controversies over his role in government action that benefited his friends and associates. The speaker has denied wrongdoing.

In an ongoing battle for positioning once DiMasi steps down, most committee chairs and rank-and-file members have sided with either Ways and Means chair Robert DeLeo or Majority Leader John Rogers. Torrisi is backing DeLeo, but said he does not expect the Winthrop Democrat to challenge DiMasi, and plans to vote "present" when the House convenes next week.

Rep. Michael Moran (D-Brighton), a DeLeo supporter, pointed to challenges to other speakers, and predicted that votes against DiMasi would fall far short of the 17 collected by Rep. Byron Rushing in his 2003 bid against Finneran. Two House members voted present that year. DiMasi made Rushing his assistant majority whip, a senior leadership post.

"I think there's going to be a few isolated incidences where people are going to, by their voting, are going to show their dissatisfaction or displeasure with the speaker," said Moran, calling the total "hard to say."

Compared to his predecessor Tom Finneran, DiMasi has notably avoided openly punitive measures, with some exceptions. He took away committee posts from lawmakers who had backed Rogers in the race to succeed Finneran, in a round of leadership changes nicknamed "The Irish Massacre" because of the ethnicity of several of the losers. After Reps. James Marzilli and Matthew Patrick dented his 2006 announcement of an energy policy package with their own more detailed plan, DiMasi downsized their committee portfolios as well.

DiMasi appears all but assured of reelection unless significant revelations about the ethics investigations emerge before next week's vote.

"Speaker DiMasi enjoys overwhelming support from the members and is proud of the House's accomplishment under his leadership, from landmark health care legislation to nation-leading energy reforms," said DiMasi communications director David Guarino. "The speaker is focused on the important issues before the House in the next session and won't be distracted from the challenges facing the Commonwealth."

One lead Rogers backer said he doubted whether Torrisi would face retribution from DiMasi, and said he planned to vote for the speaker's reelection next week.

"That's David's decision," Rep. Martin Walsh (D-Dorchester) said of Torrisi's defection. "I have not spoken to him about it. Every member has the right to vote for who they want to vote for for speaker."

A DeLeo spokesman said DeLeo planned to vote for DiMasi. A Rogers spokesman said Rogers was unavailable.