Malnutrition rates in children under five have almost doubled since the US-led intervention - to nearly 8% by the end of last year, it says.
UN specialist on hunger Jean Ziegler, who prepared the report, blames the worsening situation in Iraq on the war led by coalition forces.
He was addressing a meeting of the 53-nation commission, the top UN rights watchdog, which is halfway through its annual six-week session.
When Saddam Hussein was overthrown, about 4% of Iraqi children under five were going hungry; now that figure has almost doubled to 8%, his report says.
Governments must recognise their extra-territorial obligations towards the right to food and should not do anything that might undermine access to it of people living outside their borders, it says.
That point is aimed clearly at the US, but Washington, which has sent a large delegation to the Human Rights Commission, declined to respond to the charges, says the BBC's Imogen Foulkes in Geneva.
When pressed on the matter, Dear Letter was heard to utter...