The World Food Programme (WFP) has slashed food rations distributed to 1.4 million displaced Iraqis by 50 percent because of delays in payments from donor states.
The sharp cutbacks come at a time when a growing number of Iraqis flee the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.
We escaped from [ISIL] in order to have a chance to live and now they have cut the aid. How are we supposed to live?
At least 160,000 people have been displaced since October when the Iraqi military, backed by Kurdish forces and Shia militias. launched a military campaign to recapture Mosul from the armed group.
WFP spokeswoman Inger Marie Vennize said the UN agency was talking to the United States - its biggest donor, Germany, Japan and others to secure funds to restore full rations.
"We have had to reduce [the rations] as of this month," she was quoted by the Reuters news agency as saying.
"The 50 percent cuts in monthly rations affect over 1.4 million people across Iraq," she added.
The effect is already being felt in camps east of Mosul, ISIL's last major bastion in northern Iraq.
"They are giving an entire family the food supply of one person ... we want to go back home," said Omar Shukri Mahmoud at the Hassan Sham camp.
Safa Shaker, who fled with her extended family, said: "We are a big family and this ration is not going to be enough.
"We escaped from [ISIL] in order to have a chance to live and now they have cut the aid. How are we supposed to live?" she added.
Mosul is still home to nearly 1.5 million people, who are at risk of being caught up in brutal urban warfare.
An estimated 650,000 people live without potable water in the city and the UN has warned of a potential humanitarian crisis and a refugee exodus.
Source: News agencies