In a strongly worded 55-page report, the Senate committee also spelled out punishment options for Monserrate, who was convicted last year of misdemeanor assault against his girlfriend.
As first reported by the Daily News last month, the bi-partisan committee recommends the Senate impose one of two punishments -- expulsion from the Senate or censure with a revocation of committee and seniority privileges.
But the committee calls for separate votes on both punishments.
It's unclear when the full Senate will take up the issue.
"The Senate committee concludes and believes that sanctions against senators should only be imposed in cases of serious misconduct," the long-awaited report concludes, adding "the select committee finds that his case is serious enough to warrant a severe sanction."
Monserrate in October was convicted of misdemeanor assault against his girlfriend, Karla Giraldo.
While he was acquitted of felony charges related to the slashing of her face with a broken glass, the conviction stemmed from his dragging her down a Queens apartment building hallway.
The Senate committee said that the "nature and seriousness" of his conduct, as caught by a surveillance video and other evidence, "showed a reckless disregard for Ms. Giraldo's well being and for the severity of her injury."
The committee, made up of five Democrats and four Republicans, met six times since being formed in November and reviewed grand jury and criminal trial minutes, exhibits and testimony.
Monserrate refused to meet or cooperate with the committee. He and his lawyer have argued the Senate does not have the power to boot him and have vowed to continue showing up for work if it tries.
The Daily News reported earlier this week that Monserrate plans to seek a federal court order blocking the Senate from taking a vote, though the report says the Senate has the full power. In a statement, State Democratic Chair Jay Jacobs said that Monserrate "must resign from his Senate seat immediately."
The online blogger Gerson Borrero this morning quotes a source close to Monserrate as saying that civil rights attorney Norman Siegel will represent Monserrate.
No lawmaker has been expelled from the Legislature since the early 1920s, when five socialists were kicked out. NARAL Pro-Choice New York hailed the committee's decision Thursday.
"NARAL Pro-Choice New York is happy to see that the special Senate committee, led by Eric Schneiderman, has reached the same conclusion we did months ago: Sen. Monserrate has no business representing the women and men of New York," the group said in a statement.