The move has been heavily criticized by activists, who consider it part of the overall crackdown on free expression and political dissent in the country.
“We witnessed a shameful and ugly horror show produced by Liberman that was full of lies, ignorance and hatred worthy of the worst haters of religion and Jewish tradition of all time.”
"The real sovereignty of Israel is in the people of Israel," Rivlin said, "and the rule of law is the only law that counts."
"Liberman has taken an additional step towards his political and ethical abyss and declared clearly that he prefers to sit with members of the Joint List... rather than his brothers and sisters."
In an interview, the deputy health minister said he is suspicious of Yisrael Beytenu leader Avigdor Liberman.
Netanyahu, Gantz or someone else? Take the Jerusalem Post's poll
The News 13 poll also gave Blue and White 34 seats and Likud 33 if a third election was held now; both blocs they would lead were tied at 56, with Israel Beytenu remaining the kingmaker.
Likud’s digital campaign, which included intensive use of Facebook Live, a Facebook Messenger chatbot and aggressive tweeting, failed to bring it victory.
Netanyahu seeks to form a unity government while facing a pre-trial hearing.
Liberman stressed that the only option is a liberal national unity government.