Millions of Iraqis have little or no access to clean water, sanitation and healthcare, five years after the US-led invasion, according to the Red Cross.
The Swiss-based agency says Iraq's humanitarian situation is "among the most critical in the world".
It warned that despite better security in some areas, millions had been left essentially to fend for themselves.
Some families spend a third of their average monthly wage of $150 (£75) just buying clean water, the report found.
'Worse than ever'
An even worse humanitarian crisis in Iraq will only be averted if much more attention is paid to the everyday needs of Iraqi citizens, the report by the International Committee of the Red Cross said.
Many Iraqis still lack basic sanitation
Healthcare in Iraq was "now in worse shape than ever" and the services that are available are too expensive for many people, the report said.
Iraqi hospitals lack qualified staff and basic drugs, facilities are not properly maintained and public hospitals provide only 30,000 beds, less than half of the 80,000 needed, the Red Cross reports.
The agency said the current situation had been exacerbated for the 27m population by decades of previous conflict and economic sanctions.
The report also says that tens of thousands of Iraqis had effectively disappeared since the start of the war.
"Many of those killed in the current violence have never been properly identified, because only a small percentage of the bodies have been turned over to Iraqi government institutions," it said.
Despite security gains, many Iraqis still suffer bloodshed
Violence rates in the country have fallen 60% since last June, although the US military commander there, Gen David Petraeus, says the security gains are fragile and could be easily reversed.
But Beatrice Megevand Roggo of the Red Cross said: "Better security in some parts of Iraq must not distract attention from the continuing plight of millions of people who have essentially been left to their own devices."
Tens of thousands of Iraqis - nearly all men - are in detention, according to the agency, including 20,000 inmates at Camp Bucca near Basra, which is run by US-led multinational forces.
Iraq is the Red Cross's largest operation worldwide with an annual budget of $106m (£52m) and 600 staff.