International aid donors have failed to deliver on promises of support for Gaza after the devastating assault launched by Israel last July, says a new report by aid agencies.

The report, Charting a New Course: Overcoming the stalemate in Gaza, was released by 46 agencies including Christian Aid, Oxfam and Save the Children. It says that six months after international donors donors pledged $3.5 billion towards Gaza's recovery, many people are worse off and not a single one of the 19,000 destroyed homes has been rebuilt. 100,000 people are still homeless and many are living in makeshift camps or schools.

The report also warns that further conflict is inevitable – and with it the cycle of destruction and donor-funded reconstruction – unless world leaders implement a new approach that addresses the underlying causes of the conflict. It says that donors must insist on a permanent ceasefire, accountability of all parties for ongoing violations of international law, and an end to the Israeli blockade that seals in 1.8 million Palestinians in Gaza and keeps them separated from the West Bank.

Winnie Byanyima, executive director of Oxfam, said: "The promising speeches at the donor conference have turned into empty words. There has been little rebuilding, no permanent ceasefire agreement and no plan to end the blockade. The international community is walking with eyes wide open into the next avoidable conflict, by upholding the status quo they themselves said must change."

Christian Aid spokesman William Bell said: "We must ensure that this most recent and most devastating conflict was the last one. There must be consequences for continued violations. By facilitating a culture of impunity, the international community is committing itself to indefinitely picking up the pieces."

The report calls for reconstruction to be speeded up and for the blockade to be ended, arguing that it has reduced Gaza to dependency on aid with 80 per cent of the population receiving international assistance and 63 percent of youth unemployed.

It says that keeping Gaza separate from the West Bank has "entrenched the already problematic split between Fatah and Hamas, with enormous negative impact on the delivery of aid and services in Gaza".

The assault entitled "Operation Protective Edge" was launched by Israel on July 8, 2014, in response to rocket attacks by Hamas militants into Israel and the kidnap and murder of three Israeli teenagers by Hamas members. Around 2,132 Gazans were killed and at least 11,100 wounded, most of them civilians. Sixty-six Israeli soldiers and five civilians were killed and 69 soldiers were injured.