"Impunity, if it is allowed to persist, not only undermines justice and the rule of law but makes it all the more likely that further, grave human rights violations will be committed," said Malcolm Smart, Director of the Middle East and North Africa Programme at Amnesty International.
No one has been held accountable for the war crimes and other grave violations of international law reported by a UN Fact Finding Mission, Amnesty International and Palestinian, Israeli and international human rights organizations.
After the conflict in Gaza and southern Israel, the distinguished South African jurist Judge Richard Goldstone was mandated by the UN Human Rights Council to head a Fact Finding Mission to investigate allegations of war crimes and other violations of international humanitarian law and human rights.
In a report published last September, Judge Goldstone and his team concluded that both the Israeli military forces and Palestinian armed groups committed war crimes and possible crimes against humanity.
Following the Goldstone report, the UN General Assembly asked both the Israeli government and the Palestinian side to conduct their own investigations that are credible, independent and conform to international standards.
Amnesty International said on Sunday that if they fail to do so the international community must step in and take the measures necessary to ensure that those who perpetrated war crimes or other crimes under international law are held to account.
"There must be accountability for what happened in Gaza and southern Israel one year ago," said Malcolm Smart. "Those responsible, on both sides, cannot be allowed to evade accountability for the crimes that were committed. If the Israelis and Palestinians cannot - or will not - deliver justice themselves, the international community must ensure that the perpetrators are held to account."
Meanwhile, Gaza remains effectively cut off from the outside world by the continuing Israeli military blockade, which limits the amount of food, fuel, and other essential items that are allowed into the Gaza Strip, rendering reconstruction and recovery from the war virtually impossible.
The Israeli government launched its offensive on the Gaza Strip on 27 December 2008, with the declared aim of stopping Palestinian armed groups from firing indiscriminate rockets into southern Israel.
In the three weeks that followed, the population of Gaza was subjected to aerial and ground attacks by the Israeli military that left some 1400 Palestinians dead, including hundreds of unarmed civilians and more than 300 children.
Thirteen Israelis were killed during the conflict, including three civilians killed in rocket attacks by Palestinian armed groups.
An Amnesty International research team in southern Israel and Gaza during and in the immediate aftermath of the fighting found compelling evidence of war crimes and other serious violations by Israeli forces and by Palestinian armed groups.
The hundreds of unguided rockets fired by Palestinian armed groups at Israeli towns and villages were incapable of being directed at specific targets. They killed three civilians, injured others, damaged civilian buildings in southern Israel, and displaced thousands from their homes.
In Gaza, the Israeli military used a range of imprecise weapons and munitions in densely-populated civilian areas; these included artillery shells and mortars, and flechette shells fired from tanks.
Israeli forces repeatedly fired highly incendiary white phosphorus shells, many of which burst in the air over densely-populated areas showering people and buildings beneath with burning wedges impregnated with white phosphorus. The use of white phosphorus is strictly restricted under international law because of its highly incendiary nature; when it lands on human skin it burns deeply through the skin, muscle tissue and into the bone.
Some Israeli attacks were directed against UN compounds, including on buildings where Palestinian civilians had fled in search of sanctuary.
Many Palestinian civilians were killed with high-precision weapons which can strike with extreme accuracy, relying on surveillance drones which have exceptionally good optics, allowing those watching to see their targets in detail. Israeli officials have yet to explain adequately why so many civilians were killed in these types of attacks.
During the 22 days of the offensive, Israeli forces frequently obstructed medical care and humanitarian aid from those wounded and trapped. They prevented ambulances and medical staff from attending to the wounded and transporting them to hospital and in several cases targeted ambulance and rescue crews and others who were trying to evacuate the wounded.
Thousands of homes in Gaza as well as hospitals, schools, and the water and the electricity infrastructure were destroyed or damaged by the Israeli military.