Is there a link between the way Israel's case is presented and anti-semitism? Israel's advocates protest that behind criticisms of Israel there sometimes lurks a more sinister agenda, dangerously bordering on anti-semitism. Critics vehemently disagree. In their view, public attacks on Israel are neither misplaced nor the source of anti-Jewish sentiment: Israel's behaviour is reprehensible and so are those Jews who defend it.

Jewish defenders of Israel are then depicted by their critics as seeking an excuse to justify Israel, projecting Jewish paranoia and displaying a "typical" Jewish trait of "sticking together", even in defending the morally indefensible. Israel's advocates deserve the hostility they get, the argument goes; it is they who should engage in soul-searching.

There is no doubt that recent anti-semitism is linked to the Palestinian-Israeli conflict. And it is equally without doubt that Israeli policies sometimes deserve criticism. There is nothing wrong, or even remotely anti-semitic, in disapproving of Israeli policies. Nevertheless, this debate - with its insistence that there is a distinction between anti-semitism and anti-Zionism - misses the crucial point of contention. Israel's advocates do not want to gag critics by brandishing the bogeyman of anti-semitism: rather, they are concerned about the form the criticism takes.

If Israel's critics are truly opposed to anti-semitism, they should not repeat traditional anti-semitic themes under the anti-Israel banner. When such themes - the Jewish conspiracy to rule the world, linking Jews with money and media, the hooked-nose stingy Jew, the blood libel, disparaging use of Jewish symbols, or traditional Christian anti-Jewish imagery - are used to describe Israel's actions, concern should be voiced. Labour MP Tam Dalyell decried the influence of "a Jewish cabal" on British foreign policy-making; an Italian cartoonist last year depicted the Israeli siege of the Church of the Nativity in Bethlehem as an attempt to kill Jesus "again". Is it necessary to evoke the Jewish conspiracy or depict Israelis as Christ-killers to denounce Israeli policies?

The fact that accusations of anti-semitism are dismissed as paranoia, even when anti-semitic imagery is at work, is a subterfuge. Israel deserves to be judged by the same standards adopted for others, not by the standards of utopia. Singling out Israel for an impossibly high standard not applied to any other country begs the question: why such different treatment?

Despite piqued disclaimers, some of Israel's critics use anti-semitic stereotypes. In fact, their disclaimers frequently offer a mask of respectability to otherwise socially unacceptable anti-semitism. Many equate Israel to Nazism, claiming that "yesterday's victims are today's perpetrators": last year, Louis de Bernières wrote in the Independent that "Israel has been adopting tactics which are reminiscent of the Nazis". This equation between victims and murderers denies the Holocaust. Worse still, it provides its retroactive justification: if Jews turned out to be so evil, perhaps they deserved what they got. Others speak of Zionist conspiracies to dominate the media, manipulate American foreign policy, rule the world and oppress the Arabs. By describing Israel as the root of all evil, they provide the linguistic mandate and the moral justification to destroy it. And by using anti-semitic instruments to achieve this goal, they give away their true anti-semitic face.

There is of course the open question of whether this applies to anti-Zionism. It is one thing to object to the consequences of Zionism, to suggest that the historical cost of its realisation was too high, or to claim that Jews are better off as a scattered, stateless minority. This is a serious argument, based on interests, moral claims, and an interpretation of history. But this is not anti-Zionism. To oppose Zionism in its essence and to refuse to accept its political offspring, Israel, as a legitimate entity, entails more. Zionism comprises a belief that Jews are a nation, and as such are entitled to self-determination as all other nations are.

It could be suggested that nationalism is a pernicious force. In which case one should oppose Palestinian nationalism as well. It could even be argued that though both claims are true and noble, it would have been better to pursue Jewish national rights elsewhere. But negating Zionism, by claiming that Zionism equals racism, goes further and denies the Jews the right to identify, understand and imagine themselves - and consequently behave as - a nation. Anti-Zionists deny Jews a right that they all too readily bestow on others, first of all Palestinians.

Were you outraged when Golda Meir claimed there were no Palestinians? You should be equally outraged at the insinuation that Jews are not a nation. Those who denounce Zionism sometimes explain Israel's policies as a product of its Jewish essence. In their view, not only should Israel act differently, it should cease being a Jewish state. Anti-Zionists are prepared to treat Jews equally and fight anti-semitic prejudice only if Jews give up their distinctiveness as a nation: Jews as a nation deserve no sympathy and no rights, Jews as individuals are worthy of both. Supporters of this view love Jews, but not when Jews assert their national rights. Jews condemning Israel and rejecting Zionism earn their praise. Denouncing Israel becomes a passport to full integration. Noam Chomsky and his imitators are the new heroes, their Jewish pride and identity expressed solely through their shame for Israel's existence. Zionist Jews earn no respect, sympathy or protection. It is their expression of Jewish identity through identification with Israel that is under attack.

The argument that it is Israel's behaviour, and Jewish support for it, that invite prejudice sounds hollow at best and sinister at worst. That argument means that sympathy for Jews is conditional on the political views they espouse. This is hardly an expression of tolerance. It singles Jews out. It is anti-semitism.

Zionism reversed Jewish historical passivity to persecution and asserted the Jewish right to self-determination and independent survival. This is why anti-Zionists see it as a perversion of Jewish humanism. Zionism entails the difficulty of dealing with sometimes impossible moral dilemmas, which traditional Jewish passivity in the wake of historical persecution had never faced. By negating Zionism, the anti-semite is arguing that the Jew must always be the victim, for victims do no wrong and deserve our sympathy and support.

Israel errs like all other nations: it is normal. What anti-Zionists find so obscene is that Israel is neither martyr nor saint. Their outrage refuses legitimacy to a people's national liberation movement. Israel's stubborn refusal to comply with the invitation to commit national suicide and thereby regain a supposedly lost moral ground draws condemnation. Jews now have the right to self-determination, and that is what the anti-semite dislikes so much.

· Emanuele Ottolenghi is the Leone Ginzburg Fellow in Israel Studies at the Oxford Centre for Hebrew and Jewish Studies and the Middle East Centre at St Antony's College, Oxford

eottolenghi@hotmail.com