A key member of Naftali Bennett’s Yamina party has quit the Israeli coalition government after a row about unleavened bread during Passover, in a surprise move that leaves the prime minister without a parliamentary majority.

Idit Silman’s announcement left Bennett’s coalition, an alliance of parties ranging from the Jewish right and Israeli doves to an Arab Muslim party, with 60 seats – the same as the opposition.

“I tried the path of unity. I worked a lot for this coalition,” Silman, a religious conservative who served as coalition chairperson, said in a statement. “Sadly, I cannot take part in harming the Jewish identity of Israel.”

On Monday, Silman lashed out at the health minister, Nitzan Horowitz, after he instructed hospitals to allow leavened bread products into their facilities during the upcoming Passover holiday, in line with a recent supreme court ruling reversing years of prohibition.

Jewish tradition bars leavened bread from the public domain during Passover.

“I am ending my membership of the coalition and will try to continue to talk my friends into returning home and forming a rightwing government,” Silman said. “I know I’m not the only one who feels this way.”

Bennett’s coalition can continue ruling with 60 seats, but faces difficulty passing new legislation.

If another member of the coalition defects, however, the Knesset could hold a vote of no confidence and potentially lead Israel back to the polls for a fifth parliamentary election in four years.

Dahlia Scheindlin, a political analyst, said that if Silman “is the first person to really prepare to bring down the government, she is doing it from the place of conviction”. “She is religious, and I think we all underestimate the power of theology,” added Scheindlin.

In a formal resignation letter addressed to Bennett, Silman said: “We must admit that we tried. It’s time to recalculate and try to form a national, Jewish, Zionist government.”

After the announcement, Silman was embraced by the same rightwing politicians who had relentlessly attacked her since she followed Bennett into the governing coalition last year, reneging on election promises.

“Idit, you’re proof that what guides you is the concern for the Jewish identity of Israel, the concern for the land of Israel, and I welcome you back home to the national camp,” the opposition leader, Benjamin Netanyahu, said in a video recording.

“I call on whoever was elected with the votes of the national camp to join Idit and come back home, you’ll be received with all due honour and open arms,” the rightwing former prime minister added.

Netanyahu, Israel’s longest-serving prime minister who was in office from 1996 to 1999 and again from 2009 until last June, had vowed to play the role of spoiler against Bennett’s government, which brought an end to his years in power.

At a special session of the Knesset, which is in recess, Netanyahu said: “There is a weak and limp government in Israel today. Its days are numbered.”

The Knesset will reconvene on 8 May to resume its legislative work. To form a coalition of his own without new elections, Netanyahu would need the support of at least 61 lawmakers, which he does not have.

Bezalel Smotrich of the Religious Zionism party, once a political partner of Bennett, expressed his appreciation to Silman for her “courage to make the difficult move”, and predicted the ruling coalition would not survive her defection.

“This is the beginning of the end of the leftwing, non-Zionist government of Bennett and the Islamist movement,” he wrote on Twitter.

There was no immediate comment from Bennett, whose Yamina party now holds just five of parliament’s 120 seats.