Blue and White and Likud are currently tied on seats after the country's second election in a year.
Benny Gantz’s Blue and White coalition has ruled out a unity government with Benjamin Netanyahu as the latest election results show them neck-and-neck, with an estimated 33 seats in parliament to Likud’s 31.
A senior Blue and White leader, Moshe Yaalon, told reporters in Israel: "We will not enter a coalition led by Netanyahu."
Netanyahu made his offer on Thursday after new elections in Israel saw his Likud party tied with Blue and White, which is headed by former Israeli Defence Force chief of staff Gantz. Netanyahu had called elections to increase his majority, but the gamble spectacularly backfired.
Now neither party has the 61 seats in parliament in order to form a government and will either have to cobble together a majority with a disparate range of smaller parties, or join forces.
Avigdor Lieberman, whose Yisrael Beiteinu is expected to gain nine seats, has also endorsed a unity government and his party would likely have a role in it. But he too is reluctant to allow Netanyahu, dogged by corruption allegations which he denies, to stay on as prime minister.
The situation is further complicated by a surge in support for parties representing Palestinian citizens of Israel, which make up a fifth of the country’s population. The Joint List, headed by Ayman Odeh, has won up to 12 seats after Netanyahu's rhetoric against the Arab minority in Israel led to huge turnout.
it is not yet clear whether Israeli President Reuven Rivlin will ask either Netanyahu or Gantz to cobble together a coalition of 61 Members of the Knesset to form a government. And a result may not be imminent: Israeli law provides 28 days to form a government.
Netanyahu will fight hard for a historic fifth term, not least because losing power also means losing the judicial safe haven of high office. As a regular citizen, Bibi will no longer benefit from parliamentary immunity and could face even more scrutiny over his financial affairs and his actions while in office.