The joint list being fielded by Israeli Prime Minister Benjamin Netanyahu in this month's snap elections is continuing to lose ground to the Jewish Home faction, a new poll showed on Wednesday.

The survey, published in the daily Haaretz, still puts the list combining Netanyahu's Likud party and the Israel Beitenu faction far ahead of the opposition, three weeks before the January 22 poll.

But it found the list had slumped to an expected 34 seats in the 120-seat Knesset, down one from Haaretz's last poll, and a drop of at least three seats from early projections.

By contrast, the national religious Jewish Home party, which holds just three seats in the current Knesset, is now expected to win at least 14 seats, according to the Haaretz poll.

That puts it just behind the Labour party, which is projected to win 16 seats, down one from Haaretz's last poll.

The newspaper said Labour's narrow lead over Jewish Home, as well as the national religious party's soaring fortunes, could see the once-obscure faction become the second biggest player in the next Knesset.

That would be a stunning turn-around for the rightwing faction, which has seen a resurgence in popularity under its new leader Naftali Bennett.

Despite the surprise surge by Jewish Home, Netanyahu can still be assured another term as prime minister, with the Likud-Beitenu list far ahead of its competitors, and the rightwing bloc of parties guaranteed a clear majority.

The Haaretz poll showed the rightwing bloc winning around 67 seats to the leftwing's 53 seats.

The main uncertainty remaining is over the composition of the next government, with Netanyahu likely to have to award several posts to Jewish Home in the wake of their electoral showing.