"UNHRC gives legitimacy to murderous terror organisations like Hamas and Daash (Islamic State)," he said, accusing the rights body of overlooking "massacres" committed elsewhere in the Middle East in favour of investigating Israel for defending itself against rocket attacks from Gaza.
In response to Netanyahu's comments, a spokesman for the 47-member rights council said the inquiry it launched last month will probe both sides in the Gaza conflict.
"The resolution establishing the Commission of Inquiry clearly states the commission will investigate all violations of international human rights and humanitarian law since the current military operations began in mid-June," Rolando Gomez told AFP.
Netanyahu spoke just days after the rights council named Canadian international law expert William Schabas to run the inquiry, in a move which sparked fury in Israel, with officials denouncing him as biased.
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"Instead of investigating Hamas attacks on Israeli citizens and its use of Gazans as human shields, instead of probing the massacre (President Bashar al-)Assad is perpetrating against the people in Syria or that Daash is carrying out among the Kurds, the UN decided to come and investigate Israel, the only democracy in the Middle East ... that is acting legitimately to defend its citizens against murderous terror," he said.
The right council's commission is due to publish its findings in March 2015.
The Israeli leader accused Schabas of having "already decided" that Hamas was not guilty of anything and that there was "nothing to investigate there."
In a series of interview with the Israeli media, Schabas yesterday defended himself against allegations of bias.
Asked by Channel 2 television if he would describe Hamas as a "terror organisation," Schabas said it would be "inappropriate" to answer such a question, and urged Israel to participate in the inquiry.