A deeply divided Labor Party voted Tuesday to join the governing coalition being formed by Benjamin Netanyahu, Israel’s prime minister-designate and the leader of the conservative Likud Party.

The decision paves the way for a broader government than the narrow and hawkish one that Mr. Netanyahu would otherwise have had to settle for, increasing his chances of gaining international acceptance and possibly avoiding friction with the Obama administration.

But the move by Ehud Barak, Labor’s leader and the current defense minister, has driven a wedge between party members, a division made clear during a stormy convention on Tuesday.

Mr. Barak said that a broad government was in the national interest given the looming security challenges and the economic crisis facing Israel, and that Labor could play a more effective role as a counterforce inside the government than as a fifth wheel in the opposition.

“We do not have a spare country,” Mr. Barak told the convention, invoking the words of the revered Labor leader Yitzhak Rabin, who was assassinated in 1995. “I am not afraid of Benjamin Netanyahu; I will not serve as a fig leaf,” he added.

But some of his critics said the decision to join an overwhelmingly right-wing government would spell the end of the center-left Labor Party’s dominant role in shaping the Israeli state.

Ophir Pines-Paz, a lawmaker, said Mr. Barak did not win a mandate to throw Labor “into the garbage bin of history.”

Of the 1,187 members of Labor’s central committee who voted Tuesday, 680 supported the motion to join the coalition, and 507 opposed it.

After reading out the results of the vote, Eitan Cabel, the Labor Party’s secretary general who opposed joining a Netanyahu government, called for unity within the party ranks. But some political analysts said they expected to see a leadership battle within the party over the next few months.

Mr. Barak signed a coalition agreement with Mr. Netanyahu hours before the vote stipulating that Mr. Barak would retain the defense portfolio in the new government and giving Labor four other cabinet positions.

Mr. Barak said last month that he would take his party into the opposition after its paltry showing in the Feb. 10 elections. Labor, once a dominating force in Israeli politics, won just 13 seats in the 120-seat Parliament. Seven of those 13 members of Parliament vehemently rejected the idea of joining a Netanyahu government, arguing that Labor had to rebuild itself in the opposition.

Kadima, the centrist party led by Tzipi Livni, the foreign minister, has declined Mr. Netanyahu’s offers to join a unity government and is likely to lead the opposition. Kadima narrowly beat Likud in the elections but did not have the support of other parties to form a governing coalition.

Likud won 27 seats in the parliamentary elections and needs 61 to govern. Mr. Netanyahu has already reached coalition agreements with the nationalist party Yisrael Beiteinu, led by Avigdor Lieberman, and with the ultra-Orthodox Shas. The addition of Labor will give Mr. Netanyahu a majority, 66 seats.

Likud and Labor negotiators agreed on terms of a deal on Tuesday. The agreement was somewhat vague on issues pertaining to the Israeli-Palestinian peace process, stating that the new government would devise a plan for comprehensive peace in the Middle East; that Israel was committed to all previously signed diplomatic and international agreements; and that the government would work to reach peace accords with all of Israel’s neighbors while preserving Israel’s security and vital interests.

The agreement does not contain any mention of the two-state solution as a goal for resolving the Israeli-Palestinian conflict, but as Shalom Simhon, Labor’s chief negotiator, noted, neither does it rule that out.

Labor said it wanted a continuation of the peace process with the Palestinians but did not insist on any declaration about the two-state solution in its talks with Likud. Instead, Labor focused on socioeconomic issues in the coalition talks, a priority for much of the party’s constituency.

Mr. Netanyahu has until April 3 to complete the formation of his coalition.

Also Tuesday, clashes broke out between the police and demonstrators in the northern Israeli Arab town of Umm al-Fahm after about 100 Israeli far-rightists marched on the town’s outskirts.

The police used tear gas, water cannons and stun grenades to disperse protesters who threw rocks and rioted after the right-wing march, which lasted half an hour. Sixteen police officers, including the deputy commissioner of the national force, were slightly injured by rocks, a police spokesman said. Several protesters were also injured in scuffles with the police.

The far-rightists had been planning to march in Umm al- Fahm for months. They said they wanted to show that no part of Israel was off limits to them. The police had banned a previous march, citing threats to public order and the marchers’ safety.