Israel has declared the Nobel Prize winning poet GŁnter Grass persona non grata - after he published a work accusing Israel of posing a threat to world peace.

Nobel Prize winning poet Gunter Grass (Getty)

Controversy has surrounded Germany's greatest living writer Günter Grass, ever since his 69-line poem was published. 'What Must Be Said', which appeared in the German newspaper Suddeutsche Zeitung on Wednesday, claimed: "The nuclear power Israel is endangering a peace that is already fragile."

The verse also questioned Germany's decision to sell submarines to Israel, suggesting it risked being complicit in a crime, and condemned Western hypocrisy over Israel's threats to attack Iran over its nuclear ambitions. Asking why he was only speaking out now, at the age of 84, the poem answered: "tomorrow might be too late."

Reaction was swift: Israeli Prime Minister Benjamin Netanyahu described Grass' work as "ignorant and shameful declarations that any fair person in the world must condemn", while Israel's embassy in Berlin issued a statement offering its own version. "What must be said is that it is a European tradition to accuse the Jews before the Passover festival of ritual murder."

There was a more mixed response within Germany itself: the country's foreign minister Guido Westerwelle insisted the premise of the poem was wrong: "To put Israel and Iran morally on the same level is not intelligent, it is absurd." The newspaper Die Welt branded him "the eternal anti-Semite", in a front page spread.

Others jumped to defend Grass, defending his right to criticise Israeli policies: supporters turned out at traditional Easter peace rallies across Germany, waving banners declaring "Günter Grass is right". Predictably enough, Iran described the poem as a "literary work of human and historical responsibility".

In an interview published on Friday, Grass tried to clarify what he had meant, admitting that he should have avoided using Israel as a generic term for its current government. Benjamin Netanyahu, he said, was "the man who damages Israel the most", something he should have put into the poem. But he said he objected to "the offensive and sweeping charge of anti-Semitism" ranged against him.

However, that didn't convince Jerusalem: as Interior Minister Eli Yishai declared the poet persona non grata. "If Günter Grass wants to continue to distribute his false and distorted works," he said, "I suggest he do so from Iran, where he'll find an appreciative audience".

Grass, who won the Nobel Prize in 1999, became known as the conscience of Germany, after his 1959 novel The Tin Drum, which charted the rise of the Nazis and the start of the Second World War through the eyes of ordinary Germans. Having urged his countrymen to be open about their past, however, he only admitted in his 2006 autobiography, that he had been drafted into the Nazi Waffen-SS as a teenager, in the final months of the war.

Now his intervention into the politics of the Middle East has re-opened the highly sensitive debate about what Germans can and can't say about Israel, under the weight of its historical guilt. But mixing poetry with such a volatile situation, has taken artistic expression down a highly precarious route.