Israel’s prime minister, Benjamin Netanyahu, has said he will take on the defence minister portfolio, rejecting calls to dissolve his government even as early elections appeared increasingly likely.

Netanyahu said heading to elections now, amid repeated violent confrontations with Gaza militants, was “irresponsible” of his coalition partners, who have been pushing for early polls since the resignation last week of the defence minister, Avigdor Lieberman, over a Gaza ceasefire.

“Today, I take on for the first time the position of defence minister,” said Netanyahu on Sunday, speaking from Israel’s defence headquarters in Tel Aviv in a statement broadcast live at the start of the evening news. “We are in one of the most complex security situations and during a period like this, you don’t topple a government. During a period like this, you don’t go to elections.”

The sudden coalition crisis was sparked by the resignation of the hawkish Lieberman, who had demanded a far stronger response last week to the most massive wave of rocket attacks on Israel since the 2014 Israel-Hamas war. He alleges the ceasefire agreement reached with Gaza’s Hamas rulers will put southern Israel under a growing threat from the group, similar to that posed to northern Israel by Lebanon’s heavily armed Hezbollah.

The departure of Lieberman and his Yisrael Beiteinu party leaves the coalition with a one-seat majority in the 120-member parliament. Netanyahu’s other partners say that makes governing untenable and would leave the coalition susceptible to the extortion of any single lawmaker until elections scheduled for November 2019.

The education minister, Naftali Bennett, of the pro-settler Jewish Home party, has already threatened to bring down the government if he is not appointed defence minister. He and the justice minister, Ayelet Shaked, also of Jewish Home, will deliver a statement to the media on Monday. If the party leaves the coalition, it would strip Netanyahu of his parliamentary majority.

The finance minister, Moshe Kahlon, another senior partner, says another year of such instability will harm the economy. A meeting between him and Netanyahu on Sunday, held to convince Kahlon to stay, ended with no results.

Netanyahu’s Likud allies are already preparing to pin the blame on coalition partners if the effort to salvage the government fails.

“I think that there is no reason to shorten the term of a national government, not even for one day, and at this moment, it’s in the hands of the education minister and the finance minister,” said Gilad Erdan, the minister of public security.

No Israeli government has served out its full term since 1988. Since then, elections have almost always been moved up because of a coalition crisis or a strategic move by the prime minister to maximise his chances of re-election. Although Netanyahu has reportedly been considering the idea of moving up elections himself in recent months, though the current timing is not ideal for him.

He has come under heavy criticism for agreeing to the Gaza ceasefire, especially from within his own political base and in the working-class, rocket-battered towns in southern Israel that are typically strongholds of his Likud party. But with Lieberman forcing his hand, and the other coalition partners appearing eager to head to the polls, he may not have a choice.

Most opinion polls show Netanyahu would easily secure re-election to make him Israel’s longest serving leader, but several factors could trip him up, including a potential corruption indictment that could knock him out of contention.

Police have recommended he be indicted on bribery and breach of trust charges in two cases and have questioned him at length on another. The country has long been eagerly awaiting the attorney general’s decision on whether to press charges. Netanyahu has angrily dismissed the accusations against him, characterising them as part of a media-driven witch-hunt that is obsessed with removing him from office.