The charities made the accusation in a report published just ahead of the anniversary of Israel's offensive in the Gaza Strip. The aid agencies condemn not just Israel, but the world community.

In the words of Oxfam's director, Jeremy Hobbs, "world powers have failed and betrayed Gaza's ordinary citizens". 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.

A spokesman for the Israeli prime minister said 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, as he put it, committed to destroying Israel and killing Israelis.