The United Nations special rapporteur on the right to food has called on Switzerland to condemn "flagrant" human-rights violations by coalition forces in Iraq.
Jean Ziegler says civilian populations are being denied access to food and water in clear breach of the Geneva Conventions.
"I have formally asked Bern, as custodian of the Geneva Conventions, to intervene in order to denounce and put an end to violations of the first and second protocols," Ziegler told swissinfo. "I think the Swiss government must react."
Ziegler said he had yet to receive an answer but added that he was confident Swiss Foreign Minister Micheline Calmy-Rey would respond.
"From my experience as a special rapporteur, I know that she is determined to ensure the Geneva Conventions are respected around the world," he said.
The Swiss foreign ministry said it would respond to Ziegler's communication but had yet to receive it.
"Weapon of war"
Speaking at a press conference in Geneva on Friday, Ziegler said he had conclusive evidence that food was being used as "a weapon of war" both by coalition forces and by the insurgents.
"Given that insurgents frequently use civilian populations as human shields, the strategy of coalition forces for military assaults on cities has followed a pattern of... encouraging the civilian population to flee before the attack by cutting off their food and water supplies," he explained.
The former Swiss parliamentarian said that while he understood the military rationale behind the strategy, it was prohibited under international human rights and humanitarian law.
He said he had received reports that food deliveries were restricted to the town of Tal Afar by Iraqi and coalition forces prior to an assault in September. Water supplies were also cut off, though Ziegler admitted it was not clear who was responsible.
He said the coalition was also failing to ensure adequate supplies of food and water for civilians forced to flee to camps outside cities.
Ziegler says he intends to raise the issue of violations in Iraq before the UN General Assembly on October 27.
A spokesman for the United States military in Baghdad dismissed the criticism as untrue.
"Any accusations of coalition forces refusing the basic needs of the citizens of Iraq are completely false," Lieutenant-Colonel Steve Boylan told The Associated Press.
The UN special rapporteur, who was speaking ahead of Sunday's World Food Day, also painted a bleak picture of hunger around the world.
He said it was shocking that hunger was actually increasing despite pledges by nations to halve it by 2015 as part of the Millennium Development Goals.
According to a UN report, the number of gravely undernourished men, women and children rose in 2004 by ten million to 852 million.
Ziegler highlighted the deteriorating situation in Africa where food and famine crises had hit Niger, Burkina Faso, Mali, Sudan, Somalia, Chad, Zimbabwe, Mauritania and Ethiopia.
Effective humanitarian aid, notably food and water, also needed to reach survivors of the earthquake in northern Pakistan and India as soon as possible, he said.
He called on governments to give more, saying both the World Food Programme (WFP) and UN High Commissioner for Refugees (UNHCR) were facing funding shortfalls of $219 million (SFr282 million) and $181.5 million respectively.
"Last year military spending by the 191 UN member countries for the first time exceeded $1 trillion. At the same time funding for organisations like the UNHCR and WFP, which keep millions alive daily, was slashed. This is an absurdity," said Ziegler.
swissinfo, Adam Beaumont in Geneva
Ziegler is a former professor of social science and economics at the universities of Geneva and the Sorbonne.
He was a prominent member of the Swiss parliament's foreign affairs committee until June 1991.
He was appointed UN special rapporteur on the right to food in 2000.
Switzerland is the depositary state of the Geneva Conventions, which cover the protection of civilians and prisoners of war during armed conflict.
Under the first additional protocol to the conventions, starvation of civilians as a method of warfare is banned.
The second additional protocol prohibits the destruction of food and water necessary for the survival of civilian populations.