The international community has betrayed the people of Gaza by failing to end an Israeli blockade to allow the territory to be rebuilt, a group of 16 rights groups said in a report on Tuesday.

The report argued that Israel was in violation of international humanitarian law by enforcing a "collective punishment" with an indiscriminate blockade on Gaza - punishing all for the acts of a few.

According to the report, Israeli authorities have allowed only 41 truckloads of construction materials into Gaza since the end of its three-week offensive last January. The report added that thousands of such deliveries would be needed to repair homes.

"World powers have ... failed and even betrayed Gaza's ordinary citizens," said Jeremy Hobbs, Oxfam International's executive director.

"They have wrung hands and issued statements, but have taken little meaningful action to attempt to change the damaging policy that prevents reconstruction, personal recovery and economic recuperation," he added in a statement.

The report, compiled by 16 international and western European humanitarian and human rights groups, was released to coincide with the first anniversary of the Israeli offensive.

Reconstruction of Gaza, home to 1.5 million people, has been hampered by the Israeli blockade that stops materials such as cement and steel reaching the Hamas-ruled territory, despite billions of dollars of aid pledges.

Imposing the Gaza blockade with Egyptian help, Israel says it restricts the supply of materials that could be used for military purposes by Hamas and other armed groups which say they are bent on the Israel's destruction.

Foreign Ministry spokesman Yigal Palmor blamed Hamas for the restrictions.

"Those who want Gaza to have free access to the world should first and foremost endeavor to stop the Hamas rule of terror, so that crossings to Israel and to Egypt can be operated without fear," he said.

The report's authors urged the European Union to take immediate and concerted action to secure the lifting of the blockade.

It said that 90 percent of people in Gaza suffer power cuts of four to eight hours a day. Poor water quality was also a major concern for aid agencies, with diarrhea causing 12 percent of young deaths.

Israel launched Operation Cast Lead last December to try to suppress rocket fire. The Gaza Palestinian death toll was more than 1,300 according to a Palestinian human rights group. 13 Israeli lives were lost in the fighting.