Gaza's humanitarian situation is the worst since 1967 when Israel occupied it, says a coalition of UK-based human rights and development groups.
They include Amnesty International, Save the Children, Cafod, Care International and Christian Aid.
They criticise Israel's blockade on Gaza as illegal collective punishment which fails to deliver security.
The groups' report, Gaza Strip: A Humanitarian Implosion, says the blockade has dramatically worsened levels of poverty and unemployment, and has led to deterioration in education and health services.
"Unless the blockade ends now, it will be impossible to pull Gaza back from the brink of this disaster and any hopes for peace in the region will be dashed," said Geoffrey Dennis, of Care International UK.
The UK-based groups agree that Israel has the right and obligation to protect its citizens, urging both sides to cease unlawful attacks on civilians.
But they call upon Israel to comply with its obligations, as the occupying power in Gaza, to ensure its inhabitants have access to food, clean water, electricity and medical care, which have been in short supply in the strip.
"Punishing the entire Gazan population by denying them these basic human rights is utterly indefensible," said Amnesty UK Director Kate Allen. "The current situation is man-made and must be reversed."
Other recommendations from the groups include international engagement with the Hamas movement, which rejects Israel's legitimacy and has been shunned by Israel's allies, and the Fatah party of Palestinian West Bank leader Mahmoud Abbas.
"Gaza cannot become a partner for peace unless Israel, Fatah and the Quartet [the US and UN, Europe and Russia] engage with Hamas and give the people of Gaza a future," said Daleep Mukarji of Christian Aid.
Download the full report "Gaza Strip: A Humanitarian Implosion" here>
Also See: Guardian - Sanctions causing Gaza to implode, say rights groups