Israel’s main opposition party has split after its leader, Benny Gantz, was elected as speaker of parliament with the support of his rivals, including Benjamin Netanyahu, in a stunning plot twist to a year-long political crisis.

Gantz’s move was widely interpreted as a precursor to a power-sharing deal with the prime minister to form an emergency government. The coronavirus pandemic, including more than 2,600 confirmed Israeli cases, has added urgency to efforts to break a stalemate between the two leaders.

“These are unusual times and they call for unusual decisions. That’s why I intend to explore the formation of a national emergency government,” Gantz told the Knesset, Israel’s parliament.

While neither side confirmed that an agreement was already in place, suggested scenarios have included Gantz and Netanyahu taking turns as prime minister in a rotation system.

Whatever the outcome, Gantz took a risk by nominating himself for speaker, and he was accused of blindsiding allies and supporters in the process.

Throughout three elections, the former head of the army has run campaigns squarely focused on promises to oust Netanyahu, who faces criminal charges for alleged corruption.

Before the vote, Gantz’s public plans were to elect a speaker from his party and push through legislation to end Netanyahu’s historic political career through term limits and bans on prime ministers serving while under indictment.

That plan appears to have been abandoned by the opposition leader in favour of the complete opposite – he may now, as speaker, protect Netanyahu from such legislation to keep the possibility of a unity government alive.

However, in doing so, Gantz’s Blue and White party looks on the brink of disintegration, with factions within it refusing to back his candidacy for speaker, and several moving to break away.

Both the Yesh Atid and Telem parties, which hold more than half of Blue and White’s seats, filed to leave the alliance.

Yair Lapid, Gantz’s running mate and the head of Yesh Atid, accused the leader of surrendering “without a fight”.

“Benny Gantz decided today to break apart Blue and White and crawl into Netanyahu’s government,” he said at a press conference on Thursday evening. “We ran together because Benny Gantz looked me in the eye and said we would never sit in this bad government.”

Tamar Zandberg, a member of the leftwing Meretz party allied with Blue and White, accused Gantz of abandoning millions of voters who sought an alternative to Netanyahu.

“You’ll end up a rug under the feet of an alleged crook, an inciter and racist,” she said in a speech to the session. “We are overwhelmed by the depth of the deceit and disgrace that has plagued today.”

In his speech, Gantz said he would “never compromise on the principles underpinning the votes of over a million Israelis who voted for Blue and White. I will never compromise on democracy. Netanyahu is well aware of that.”

While a unity government was not confirmed, a member of Netanyahu’s rightwing bloc, the defence minister Naftali Bennett, publicly congratulated Gantz for what he said was “the brave step of entering into a unity government under Netanyahu”.

Israel’s previous speaker, Yuli Edelstein, was a close ally of Netanyahu and a member of Likud. He resigned on Wednesday following fierce criticism of his refusal to open parliament, which he suspended last week citing a ban of large gatherings while the country tackled the coronavirus.

The suspension was decried as an anti-democratic attempt to shield his job and to protect Netanyahu from bills that could oust him.

For the past year Israel has been in a state of political paralysis as a result of three inconclusive elections, the latest of which was held on 2 March. In that time both Netanyahu and Gantz have been picked to form governments and failed. Throughout the crisis, Netanyahu has remained interim prime minister.

Gantz was the latest to be tasked with forming a government after gathering a loose coalition of anti-Netanyahu Knesset members to back his candidacy. However, it was not clear if he had the votes to build a solid, majority coalition by the mid-April deadline.

Israel’s president, Reuven Rivlin, has been urging the two leaders to form a unity deal.