Israel's ultra-Orthodox parties, already at odds with coalition partners over demands to draft young religious men into the army, are again testing the unity of Prime Minister Benjamin Netanyahu's government with a challenge over education funding.

The latest rift centres on an ultra-Orthodox push for schools in their separate education system to receive the same benefits as state-run schools, especially their "New Horizon" programme that adds school hours and sharply hikes teacher pay.

"For a year we have been fighting for the entry of 'New Horizon' into ultra-Orthodox institutions. There is no reason for our teachers to be discriminated against," said ultra-Orthodox Education Minister Haim Biton.

Biton, a member of Shas, one of two Orthodox parties in the right-wing coalition, said they would not quit the government over the issue. But the other ultra-Orthodox party, United Torah Judaism (UTJ), notified the coalition whip that until the funding issue was resolved it would boycott votes in parliament.

Coalition whip Ophir Katz said he was working to avert a showdown ahead of a vote on a 3.4 billion shekel ($918.35 million) budget boost to help fund tens of thousands of Israelis displaced from their homes by rocket fire from Lebanon.

The dispute is the latest of many that have highlighted both the tensions within Netanyahu's unwieldy coalition through almost two years of near-constant crisis punctuated by mass protests against judicial reforms and the Gaza war.

With a grouping of religious and hardline nationalist-religious parties and his own right-wing Likud party, Netanyahu controls 64 of parliament's 120 seats but from the start, relations between ministers have been fractious.

Far-right parties led by Finance Minister Bezalel Smotrich and National Security Minister Itamar Ben-Gvir have repeatedly shaken the coalition over issues including the handling of the Gaza war, threatening to leave over any move, backed by Defence Minister Yoav Gallant, toward a deal to end the conflict.

The ultra-Orthodox parties have been less vocal about the conduct of the war but have fought hard for benefits for their Haredi community, who comprise around 13% of the population.

Tensions have run especially high over the recent abolition of an exemption long enjoyed by Haredi men from conscription into the military under a ruling by the Supreme Court, but the education budget has also caused problems.

"The Haredi parties feel that the extreme right secured all of its demands from the government and Ben-Gvir gets whatever he wants from the prime minister, while they are failing," said Gilad Malach, director of the Israel Democracy Institute's ultra-Orthodox programme.

With Netanyahu's government likely to face a reckoning at the polls over the security failures that allowed the Oct. 7 cross-border attack by Hamas from Gaza to happen, none of the parties have shown any real inclination to walk out.

But even so, such tensions contain the seeds of future problems, Malach said. "It might begin a process that all parties don't want right now but that might be the result."