The results of last week's parliamentary elections in Israel brought to the surface some of the most rotten fruits of a debate that has been going on throughout the state's existence: the idea that a mono-ethnic Jewish state is feasible, legitimate and desirable. In other words, it enhanced the predicament of the moral and practical consequences of the Zionist state ideology.

In 1948, during its war of coming-to-be, Israel had driven out of its territory 750,000 Palestinians; another 250,000 were pushed out during the 1967 war. Ever since then, the Israeli left-right division has been marked by the desire for territorial expansion, promoted by the right, and the aspiration for ethnic purity, propagated, curiously, by the Zionist "left". It has always been the "left" that pushed for "division" of the land and "separation" between Jews and Arabs in order to secure a big Jewish majority inside Israel. The right, historically, seemed unconcerned by and large with the consequences of having a large number of Palestinians living under Israel's occupation, as long as they do not get to enjoy citizens' (or other, civil) rights. The Labour party always had a leg in both camps. It had agreed to partition in 1947, seeing it as a chance to get as much Arab-free land as possible, and recognising the opportunity to ethnically clear it off most remaining Arabs during the following war. It was the same Labour party, however, that was responsible for Israel's great victory in the 1967 war, which led to vast territorial expansion and at the same time to the inclusion of millions of Palestinians in the territories under Israel's rule.

An annexation of these territories, known as Gaza Strip and the West Bank, has always been unthinkable for the Labour party and its satellites on the left, as it would involve granting citizenship to the Palestinians who live in them, hence compromising the majority of Jewish citizens in Israel. The right had toyed with the idea of annexation, but was deterred by the same dilemma. The temporary solution had been to keep building settlements in the occupied West Bank and Gaza, while hoping that somehow, miraculously, the Palestinians would disappear, or that a huge influx of Jewish citizens would somehow flood the country and tip the balance in a conclusive way.

In the fringes of the left there were always voices calling for either a viable Palestinian state alongside Israel. To its left, there was an even smaller group calling for what nowadays can be described as the South African solution: one state, with equal rights to both Jews and Palestinians living in it.

The latter idea had never become popular among Jewish Israelis, but over the last 10 years it had turned into a threat that haunts the dreams of all Zionists. The phrase "the demographic danger" became a legitimate part of the discourse calling for a two-state solution. What started as a lefty support for Palestinian national self-determination had turned in this century into a tool for propagating apartheid. From that point, it was easy for anybody on the right, from Ariel Sharon to Tzipi Livni and Binyamin Netanyahu, to adopt it, and for George Bush's administration to embrace it. Accordingly, that obscure entity the "Palestinian State" was to be of crippled borders that would compromise its already questionable viability. It was to be a http://en.wikipedia.org/wiki/Bantustan Bantustan.

The Arab citizens of Israel, traditionally ignored by left and right Zionists as a "barely tolerable" minority, embody the impossibility and futility of the attempt to achieve ethnic purity by means of division. A few years of rising racism inside Israel turned its Arab citizens into a "ticking bomb" of the "demographic danger", and unleashed unprecedented attacks against them by the right wing, with little to no response from the Zionist left. Avigdor Lieberman gained his startling achievement in Tuesday's elections by riding this wave to its natural conclusion. His revolutionary idea – giving up not only territories in the West Bank and Gaza but even territories of Israel proper, in order to get rid of as many Arabs as possible – confused and embarrassed the Zionist left. It had also exposed the absurdity and moral unacceptability of the whole Zionist idea by taking it to its only rational conclusion. If having a Jewish state is the most desirable goal, than getting rid of the non-Jewish citizens is the only rational way to go about it. And hey, it is all to take place in a very benign way: no more talks of "transfer", but an adoption of the "lefty" slogans of division. And all this under the new sinister banner "No loyalty – No citizenship".

The fact that Lieberman can easily claim to be a genuine successor of Israel's founder, Labourite David Ben Gurion, should be an alarm bell in the ears of any Israeli liberal. It is time for any Israeli with an enlightened self-image to look at the mirror and see Avigdor Lieberman staring back. It is time to stop the procrastination over the question whether Israel can be both Jewish and democratic. Lieberman provided the answer loud and clear: it cannot. At this late hour, when the shadow of proto-fascism is hovering over the land, it is time to join forces with Palestinian citizens in the battle against ethnic purity, and for a true democracy. It is time to stop fidgeting, and to admit that mono-ethnicism cannot be a framework for liberal values. It is time to apologise to MK Azmi Bshara, who was dabbed "an Arab nationalist" by Israeli liberals because of his call for "a state of all its citizens". It is time to rethink Zionism.