Prime Minister Benjamin Netanyahu rebuked his combative foreign minister on Tuesday for attacking members of the Israeli leader's Likud party, pointing to growing strains within Israel's coalition government.

In a rambling press conference, Avigdor Lieberman criticized Likud leaders for opposing an initiative to investigate Israeli human rights groups critical of the government. He said it was a "strange spectacle" to see Likud members protecting groups that he described as "terrorist collaborators."

Netanyahu's office said the prime minister "utterly rejects" the comments, reminding Lieberman that Likud is a "democratic and pluralistic party and not a dictatorship of one opinion."

Lieberman, who immigrated to Israel from the former Soviet Union, leads the Yisrael Beitenu party, which made strong gains in 2009 elections with a nationalist message that, among other things, questioned the loyalty of Israel's Arab minority.

Lieberman more recently has turned his attention to Israeli human rights groups, pushing parliament to launch an inquiry into funding sources of organizations deemed hostile to Israel. In particular, he is targeting groups that have helped seek prosecution of Israeli soldiers for alleged war crimes during battles against Palestinian militants.

Critics say Lieberman's proposal would stifle dissent and limit democracy. Several senior Likud members reject the move, saying it is not the parliament's job to impede public debate.

Tuesday's comments were not the first time Netanyahu has had to rein in his cantankerous foreign minister.

Lieberman has embarrassed Netanyahu with his repeated skepticism on the chances of reaching peace, including a high-profile speech at the United Nations General Assembly last September in which he contradicted Netanyahu's stated goal of reaching a final peace deal in the coming year.

Lieberman has also proved a distraction with his repeated attacks on Arab lawmakers, and by pushing through a law that would require non-Jewish immigrants to take a loyalty oath before becoming citizens. That proposal was widely seen as racist and anti-Arab because it would not require Jewish immigrants to take the oath.

In other challenges facing the government, the centrist Labor Party last week threatened to pull out of the governing coalition within months if no significant progress was made in peace talks with Palestinians.

On Tuesday, Labor lawmaker Daniel Ben Simon said he was leaving the party and becoming an independent in parliament. He said the step was to protest Labor's continued presence in the coalition.