Tony Judt, a former Oxford history don, writes in the current issue of The New York Review of Books, a scholarly journal, that if Israel keeps control of the occupied territories without resorting to unacceptable ethnic cleansing, its Jews will soon be outnumbered by disenfranchised Arabs.

“It is time to think the unthinkable,” he writes. “Unless something changes, Israel in half a decade will be neither Jewish nor democratic.”

Judt, a liberal Jew and former kibbutznik who previously supported the creation of a Palestinian state alongside Israel, now says that the Middle East peace process is “finished” and that the notion of a two-state solution is “probably already doomed”.

The response from supporters of Israel has been furious. David Frum, former speech writer for President George W Bush and who helped to invent the term “axis of evil” to describe Iraq, Iran and North Korea, has denounced Judt’s article for “genocidal liberalism” that would expose Jews to slaughter and exile. While his views may sound “outlandish” to Americans, Frum warns, they represent a “growing consensus” in Europe.

Judt lives in America where he is a professor of European studies at New York University. He watched the World Trade Center burn from his window on September 11, 2001, and wrote then that he had witnessed the birth of the 21st century.

However, he argues that Bush is drawing America into a widening Middle East conflict that meets the objectives of Israel’s foreign policy but is of little use against Al-Qaeda. “Which war are we fighting?” he asks.

Judt concludes: “The depressing truth is that Israel’s current behaviour is not just bad for America, though it surely is. It is not even just bad for Israel, as many Israelis silently acknowledge. The depressing truth is that Israel today is bad for the Jews.”

John Podhoretz, a neo- conservative commentator, said: “It is the definition of intellectual corruption to say I don’t like the way things are, so I’m going to wish them away.” A bi-national state was “unthinkable, like assembling Yugoslavia in the middle of the Bosnian war with the Serbs”.

Perceived attacks on Israel tend to provoke a strong response in America, particularly in New York, which has the largest concentration of Jewish people outside Israel.

Leon Wieseltier, an old friend of Judt, has written perhaps the most wounding denunciation of Judt’s arguments in The New Republic magazine. Calling the article “haughty and ugly”, he writes: “Judt and his editors have crossed the line from criticism of Israel’s policy to criticism of Israel’s existence.”

Wieseltier said Judt’s views came “almost as a personal blow to me”. He believes that Judt has grown tired of being attacked for Israel’s behaviour. “I detect the scars of dinners and conferences. He does not wish to be held accountable for things he has not himself done. Judt is embarrassed by Israel. And so Israel must be gone.”

A strong supporter of a two-state solution to the crisis in the Middle East, Wieseltier said: “Tony and I are both hoping our friendship survives.”