Opposition politicians slammed Mr Netanyahu's new campaign slogan - "A strong leader for a strong nation" - as a rallying cry reminiscent of Nazism.

"This slogan recalls those used by the Nazi Third Reich and is an insult to the survivors of the Holocaust," said Abraham Burg, a Labour Party member and chairman of the Jewish Agency, a quasi-state body.

'Hollow'

A rallying cry or an insult?

Another Labour leader, Shlomo Ben Ami, accused Netanyahu and his Likud party of "reviving the spectre of fascism".

Labour leader and leading contender for prime minister, Ehud Barak, said: "This is a hollow slogan for a prime minister who is incapable of bringing peace and security or battling unemployment."

Correspondents say the opposition criticism of the electoral slogan - which was unveiled on Sunday - indicates that the left is already appealing to Israel's historical fears of the far right.

Defections

Mr Netanyahu rejected calls to drop the slogan and accused the Labour Party of "using the method of totalitarian regimes to libel and deny me any legitimacy".

Mr Netanyahu's political group, Likud, has dismissed the criticisms as politically motivated and says it is planning to put up thousands of posters bearing the slogan around the country.

But BBC Correspondent Hilary Andersson says key defections from Mr Netanyahu's party, including former defence minister, Yitzhak Mordechai, have left Likud looking considerably more right-wing.

The defectors have since joined a new centre party, which is battling to find an identity distinguishing it from Likud or Labour.

JFK-style campaign

Mr Netanyahu said: "This is a great slogan which says clearly that Israel needs a leader who is able to resist outside pressure and that the Labour Party can't provide this."

The prime minister, whose campaign is being devised by a American consultant, Arthur Finkelstein, claimed his slogan was modelled on those used by John Kennedy and Ronald Reagan.

But historian Zeev Sternhell, a specialist in the Third Reich, rejected such comparisons. "This kind of slogan sends shivers up the spine," he said.

'Israeli approval'

Mr Netanyahu's campaign team "must have carried out opinion polls and concluded that this slogan would be well received by the Israelis, and that is particularly worrisome," he added.

The Israeli press noted the slogan's similarities to language used by the Israeli far-right when it tried to prevent the Wye River land-for-security agreement with the Palestinians in October.

Jewish settlers and other ultra-nationalists opposed to peace accords used the slogan, "Netanyahu will not give in, the people are strong."

Israelis will cast separate ballots on 17 May to elect a prime minister and a new parliament.

If none of the prime ministerial candidates gets 50% of the vote, a second-round run-off between the two leading contenders will be held on 1 June.