BOSTON —The Massachusetts House of Representatives on Thursday expelled state Rep. Carlos Henriquez, who is serving a six-month jail sentence after being convicted of assaulting a former girlfriend.

The expulsion, approved by a 146-5 vote after less than two hours of debate, took effect immediately. It was the first time in nearly a century that House lawmakers expelled one of their own.

Before the vote, Henriquez told the chamber he was innocent of the charges and rejected calls for him to resign.

“You may have thought, or think, that this could have been avoided if I resigned, but with all due respect, it is my strong belief that an innocent man does not plea, an innocent man does not quit,” he said.

Henriquez, who was brought to the Statehouse by sheriff’s deputies, also questioned the fairness of his trial and sentence.

“My reputation has been attacked and severely damaged, my livelihood and freedom taken, my character forever called into question,” he said. “The truth is I never touched my accuser in any way, at any point in time, that would result in harm or injury.”

Henriquez wore a dark suit and wasn’t handcuffed during a six-minute speech. He left the chamber immediately after speaking and was not allowed to vote.

Members of the House Ethics Committee said lawmakers need to be held to high standards. They also noted that Henriquez would be unable to cast votes while incarcerated and couldn’t fully serve his constituents.

“As public officials and figures and especially as elected officials we are held to the highest level of scrutiny, as we should be,” said committee acting Chairman Rep. David Nangle.

A number of lawmakers who spoke in favor of expelling Henriquez said his conviction and decision not to resign left them with no other option. “We are doing what we have to do because we have no choice,” said Theodore Speliotis, D-Danvers.

Lawmakers also rejected an amendment that would have censured Henriquez instead of expelling him.

After weeks of secretive deliberations, the ethics committee filed a report Tuesday night that found Henriquez violated a key House ethics rule and shouldn’t be allowed to keep his seat.

Henriquez faulted the report for what he called “careless or intentional ambiguity, the blending of accusation and facts.”