Four percent of Iraqis under age five went hungry in the months after the former president's ouster in April 2003, and the rate nearly doubled to 7.7% last year, said Jean Ziegler, the UN Human Rights Commission's special expert on the right to food.
The situation is "a result of the war led by coalition forces", he said.
Overall, more than a quarter of Iraqi children do not get enough to eat, Ziegler told the 53-nation commission, the top UN human rights monitoring group.
The US delegation did not respond to the report, and diplomats at the US mission to the United Nations' European headquarters in Geneva said they would not comment.
Ziegler cited an October 2004 US study estimating that as many as 100,000 more Iraqis, many of them women and children, had died since the start of the US-led invasion than would have been expected otherwise, based on the mortality rate before the war.
"Most died as a result of the violence, but many others died as a result of the increasingly difficult living conditions, reflected in increasing child mortality levels"
Jean Ziegler, UN Human Rights Commission's special expert on the right to food
"Most died as a result of the violence, but many others died as a result of the increasingly difficult living conditions, reflected in increasing child mortality levels," Ziegler said.
Earlier, the British-based Lancet medical journal raised controversy when it published a report that said more than 100,000 civilians had died since the US-led invasion.
The authors of the report in The Lancet, researchers from Johns Hopkins University, Columbia University and the Al-Mustansiriya University in Baghdad, conceded their data was of "limited precision" because they depended on the accuracy of the household interviews used for the study. The interviewers were Iraqi, most of them doctors.
Ziegler also told the human rights commission he was concerned about hunger in North Korea, Palestinian areas, Sudan's conflict-ravaged Darfur region, Zimbabwe, India, Myanmar, the Philippines and Romania.
Worldwide, he said, more than 17,000 children under age five die daily from hunger-related diseases.
"The silent daily massacre of hunger is a form of murder," Ziegler said. "It must be battled and eliminated."