The report comes just days after a spate of Israeli raids left more than 120 Palestinians dead.
It also said that hospitals are suffering from power cuts of up to 12 hours a day, and the water and sewage systems were close to collapse, with 40-50 million litres of sewage pouring into the sea daily.
The organisations called on Israel to end its blockade of Gaza and for both sides to stop cease cross-border attacks.
Kate Allen, the UK director of Amnesty international said: "Israel has the right and obligation to protect its citizens, but as the occupying power in Gaza it also has a legal duty to ensure that Gazans have access to food, clean water, electricity and medical care.
"Punishing the entire Gazan population by denying them these basic human rights is utterly indefensible. The current situation is man-made and must be reversed."
Israel removed settlements and withdrew its forces from inside Gaza in 2005 but maintains control of most of Gaza's land, sea and air access.
After inter-Palestinian fighting left Hamas in de-facto control of Gaza in June, Israel closed the territory's borders, allowing only shipments of vital goods into Gaza.
Israel's defence ministry rejected the report, blaming Hamas for the hardships in Gaza.
"The main responsibility for events in Gaza - since the withdrawal of Israel from the territory and the uprooting of the settlements there - is the Hamas organisation, to which all complaints should be addressed," Major Peter Lerner, a defence ministry spokesman, said in a statement.
The Israeli defence ministry also said medicines and medical equipment are shipped into Gaza with no limitation. On Wednesday, the military said it allowed 69 truckloads of supplies into Gaza, including basic food and baby formula.
However, Zahir Janmohamed, the Middle East advocacy director for Amnesty International, told Al Jazeera: "The Israeli government needs to lift the blockade, humanitarian assistance is not reaching Palestinians and if things continue the way they are, then I'm worried that even more chaos will erupt."