According to Israel's Channel 10, one of Netanyahu's top aides on Wednesday assured Aryeh Deri, whose religious Shas party is seen as the kingmaker in Israeli politics, that Yair Netanyahu and Sandra Leikanger "only study together".
Deri had previously joined a chorus of condemnation that had followed reports that Yair Netanyahu, 23, was in a relationship with Sandra Leikanger, a 25 year old from Grimstad in southern Norway.
"Shame on the people of Israel that the son of the prime minister maintains a relationship with a gentile," he had said in an interview on Israeli radio. "I know friends of mine who invest tens of millions and more, hundreds of millions, to fight assimilation in the world. If, God forbid, it's true, woe be unto us."
Leikanger met the prime minister's son at the Interdisciplinary Center in Herzliya, where they both study.
According to Norway's NTB newswire, Netanyahu referred to Leikanger as his son's "girlfriend" in a casual conversation with the Norwegian press before a formal meeting with the country's Prime Minister Erna Solberg in Davos last week.
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But after the relationship was reported in Norway, it has become a major scandal in Israel.
"Bibi's son has found a Gentile. His father is proud of him and is thereby supporting the destruction of the Jewish state," Lehava, a group working against marriage between Jews and non-Jews, wrote on its website.