"There is no question that Hamas is part of the jihadist universe," said Dore Gold, incoming director general of the foreign ministry and former ambassador to the United Nations.
"It is not a candidate to become a political partner," he told journalists as his conservative think-tank, the Jerusalem Centre for Public Affairs, unveiled a study of the 2014 war in Gaza, where Hamas is the de facto power.
Gold was named to the foreign ministry post last week by Netanyahu, who has retained the ministerial portfolio himself.
The position of deputy foreign minister is held by an ultra-Orthodox MP from the far-right fringe of Netanyahu's ruling Likud party.
Last week, President Reuven Rivlin appeared to challenge a longstanding taboo on talks with Hamas, saying he would talk to anyone.
"It is really not important to me with whom I speak, but rather about what we are speaking," he said, asked his opinion about talking with the militant group.
"I have no aversion to holding negotiations with anyone who is prepared to negotiate with me," he said.
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"Hamas has been rigidly ideological and refuses to jettison the Hamas charter and its ideological positions," Gold said, referring to its founding document which is committed to Israel's destruction and rejects the idea of peace talks.
"I don' see them as being a candidate for real diplomacy in the future."
Last year's deadly 50-day war in and around Gaza claimed the lives of more than 2,200 Palestinians, most of them civilians, and 73 people on the Israeli side, most of them soldiers.
The fighting ended on August 26 with an informal truce has been largely observed, although there are growing fears of a new outbreak of violence in and around the coastal territory which has seen three wars in the past six years.
After the conflict ended, Gaza's former Hamas premier Ismail Haniya pledged there would be "no direct negotiations with the Zionist enemy".
Netanyahu has described Hamas, along with the Islamic State jihadist group, as "branches of the same poisonous tree".
Gold also accused Hamas of allowing Al-Qaeda linked groups to operate inside Gaza.
"Some people try to portray the Al-Qaeda affiliates that operate in Gaza as opposition to Hamas," he said. "I believe that Hamas fully acquiesces to their presence in the territory."