The rightwing alliance between Israeli Prime Minister Benjamin Netanyahu and his foreign minister has polarised political forces in Israel ahead of next January's parliamentary election.

Netanyahu and Avigdor Lieberman's surprise announcement late on Thursday that their respective Likud and Yisrael Beitenu parties would run on a joint ticket was dubbed "the rightwing Big Bang" by the Israeli press.

Alongside the ultra-nationalist Yisrael Beitenu, the premier's right-wing Likud -- already predicted to win the vote -- would be able to form a broad nationalist bloc leaning strongly to the right.

Such a move would also allow Netanyahu to overcome, to some degree, the chronic instability of past coalition governments in the country.

"Israel needs a strong coalition government based on a political list based on genuine cooperation," Netanyahu said on Thursday evening.

"We ask the people to support strengthening the state, and I want a clear mandate so I can take care of the basic" issues.

Israeli media quoted a survey by an adviser to Lieberman, according to which the joint list would receive 51 seats in the 120-seat Knesset, or parliament, when the votes are cast on January 22.

Other polls, however, predict an outcome of less than 42 seats, the current combined number of Likud (27) and Yisrael Beitenu (15), the third largest political force in the Knesset.

"We are not worried about the polls, what interests us is the construction of a broad nationalist camp," Lieberman said at a news conference on Friday.

"Israel must move away from a reality of many parties to a system of larger parties. We will probably never reach two, like in the United States, but must achieve a system of four or five parties to ensure governmental stability," he added.

Assuming his expected victory takes place, Netanyahu is certain to remain premier.

But the Likud has vehemently denied a report of a premiership rotation deal with Lieberman, a populist authoritarian certain to receive a key position in the future cabinet.

The leaders of the political centre and left denounced the "nationalist" and even "racist" Likud.

Lieberman, a settler who was chief of Netanyahu's staff during his first term as prime minister in the late 1990s, is famous for his anti-Arab and nationalistic statements.

"The demon is out of its nationalistic closet. Netanyahu has removed his mask," the leader of the centre-right Kadima party Shaul Mofaz told public radio, calling on the centre to unify.

"Bibi" Netanyahu and Lieberman's together might "encourage the centre-right parties to announce close cooperation in a national salvation front," wrote Yossi Sarid, former Knesset member for the left-wing Meretz party in a column in left-leaning daily Haaretz.

Such a front would have "but a single mission: no to 'Biberman'."

Speaking on public radio, Labour chief Shelly Yachimovich called for the creation of a "centre-left bloc, consisting of the centrist parties and moderate members of the Likud."

In recent weeks media have noted the ambitions of potential candidates, such as former prime minister Ehud Olmert and former foreign minister Tzipi Livni, to head a centrist bloc to compete with Netanyahu.

The Likud-Yisrael Beitenu alliance also threatens the orthodox parties, which could lose the pivotal role they have wielded in past coalitions, and they could even be excluded from the next one.

According to commentators, Netanyahu's pact with Lieberman's pact with Lieberman implies the adoption of at least some of Yisrael Beitenu's platform.

Its policies include military conscription of rabbinic seminary (yeshivot) students and reducing the power of the Chief Rabbinate on matters such as conversions.

The Israeli parliament decided earlier this month that the election would be held on January 22, 2013, nine months before its scheduled date.