The charities call for more pressure to be exerted on Israel to end what they describe as its illegal collective punishment of Gazans.

Israel imposed a tightened blockade after the Islamist Hamas movement seized power two-and-a-half years ago.

That was bad enough, say the aid agencies.

Matters became that much worse after the destruction caused by the Israeli offensive in Gaza earlier this year.

The report points to an acute shortage, in particular, of building materials.

A spokesman for the Israeli prime minister told the BBC that Israel remains committed to humanitarian supplies of food, medicine and power.

But he said that sanctions will remain in place as long as Hamas is committed to destroying Israel and killing Israelis.