A United Nations investigation into the Gaza conflict will be used as a political weapon to undermine Israel and could lead to an upsurge of international antisemitism, the head of a Geneva NGO has warned.

Hillel Neuer, director of the highly respected UN Watch, has said the group is preparing to challenge the report, which is due to be formally presented to the UN Human Rights Commission at the end of the month.

It is widely believed that the report will result in calls for Israel to be prosecuted for alleged war crimes.

Although the document, which was being completed this week, is also expected to criticise Hamas rocket attacks on Negev towns and villages, this is unlikely to be “the big story”, Mr Neuer argued, considering the allegations likely to be levelled against Israel.

Mr Neuer, in London to address the Zionist Federation’s annual meeting, has repeatedly questioned the impartiality of the fact-finding mission, headed by South African judge and war crimes prosecutor Richard Goldstone.

Mr Neuer’s claim that some of the mission’s members, including London School of Economics law professor Christine Chinkin, had pre-judged Israeli guilt was recently dismissed by the UN’s Human Rights Commission.

Mr Neuer said that the fact Judge Goldstone was Jewish was “a major factor in him being chosen to lead the inquiry. There is a danger that this will be used to show that the report is balanced.”

Describing the UN as “an upside down, absurd and false world”, Mr Neuer said: “(Judge) Goldstone is not a stupid man but I think he believes the ends justify the means, that what he is doing is bringing peace to the Middle East. He is wrong.”

Mr Neuer pointed out that Israeli culpability has already been assumed by some UN officials. Human rights chief Navi Pillay has already announced that if the inquiry found evidence of war crimes, they should be investigated by the International Court in the Hague.

UN Watch, whose causes also include Darfur and political prisoners in Cuba, was preparing for the report to be turned into a “snowball to take Israel to the International Court”, warned Mr Neuer. “It will be a political weapon to target Israel and stop it protecting its rights. It will bring forward a campaign to demonise it and isolate it.”

The main question, he continued, was why Israel was not treated equally at the UN. Why, he asked, were some 80 per cent of the Human Rights Commission’s statements on humanitarian abuse about Israel and the Palestinians when there were “far worse examples” worldwide?

“I would say that the UN in Geneva is the place where the new antisemitism is much in evidence. Today it is dressed up as human rights but it sees Israel as the collective Jew. We have blood libels and the demonisation of Israel as the enemy of humanity. The UN has become ground zero for the deligitimisation of Israel.”