The report looked at eight attacks on family homes in Gaza, which caused the deaths of at least 104 civilians, including 62 children.
Amnesty said that several of the attacks "directly and deliberately targeted civilians or civilian objects, which would constitute war crimes." Palestinian armed groups also committed war crimes, the NGO said, deliberately targeting civilians in Israel and killing six civilians including one child.
The investigation into the two-month offensive, named Operation Protective Edge, was conducted from outside Gaza by the charity, working with researchers in the territory. No staff from the NGO were permitted access into the Gaza Strip, Amnesty claimed.
One of the bombings killed 36 members of four families, including 18 children, who died when their homes in the three-storey al-Dali building in the city of Khan Yunis were completely destroyed.
Another attack killed 25 members of a family, 19 children, five women and one man, though the report noted that a member of the al-Qassam Brigades, the apparent target, was in the vicinity of the house and was also killed.
Amnesty said that although it acknowledges the two of the eight attacks had a military purpose, they were "grossly disproportionate and under international law they should have been cancelled or postponed as soon as it was evident that numerous civilians were present in the houses". Of the others, Amnesty said it could find no link to militant activity at all.
Israel has repeatedly said that it drops leaflets warning of attacks and widely publicises where it will attack to warn civilians to get out. But Amnesty said that in all of the cases it researched "no prior warning was given to residents of the homes which were attacked - if warnings had been given excessive loss of civilian life could have been avoided".
“Israeli forces have brazenly flouted the laws of war by carrying out a series of attacks on civilian homes, displaying callous indifference to the carnage caused," Amnesty International Middle East and North Africa Director Philip Luther said.
“It is tragic to think that these civilian deaths could have been prevented. The onus is on Israeli officials to explain why they chose to deliberately flatten entire homes full of civilians, when they had a clear legal obligation to minimise harm to civilians and the means of doing so.
“Even if a fighter had been present in one of these residential homes, it would not absolve Israel of its obligation to take every feasible precaution to protect the lives of civilians caught up in the fighting.
“What is crucial now is that there is accountability for any violations of international humanitarian law that have been committed. The Israeli authorities must provide answers.”
Khalil Abed Hassan Ammar, a 45-year-old doctor with the Palestinian Medical Council, saw three of his four children killed as they watched television early in the evening
“I heard the whistle of the missile before it hit. We felt it was really loud and realized it was going to hit us, or our building. It went into my kids’ bedroom. We were sitting with our guests in the living-room, my wife was making iftar in the kitchen and the kids were playing in their bedroom. It turned out that we were hit with two missiles. All of a sudden after the hit and after we realised what had happened, we couldn’t hear the kids; their voices had completely gone that’s when I realised they were all dead. The apartment was totally dark, full of smoke and a poisonous smell – we could hardly breathe.
“It was terrifying; we couldn’t save anyone. We inhaled so much of the intoxicating smell that we couldn’t do anything, so other people came inside and pulled out the dead bodies.
"All of the kids were burnt. I couldn’t tell which were mine and which were the neighbours’ – they were all in my apartment. Some of them were blown outside of the building through the windows and balconies. It was impossible to recognize them or their features.
"We carried whoever we were able to the ambulance. I got to the hospital and I felt that not all my kids were there and someone was missing. I only recognized Ibrahim, my eldest child, when I saw his leg and the shoes he was wearing. I had bought them for him two days before everything happened. It wasn’t the whole body; it was only pieces but I recognised his leg from his trousers.
“When we went back to the building, there was rubble from our building in one of the houses east of it. I found the body of a little kid that was totally burned and thought he was mine. My wife said it wasn’t him. I stayed in the house and contacted the civil defence and ambulance, but they were not picking up the phone. Two of my dead kids were kept out of the morgue refrigerator because it was full – they were on the ground with tens of bodies from other families. I decided to stay there with my kids.”
Khalil’s wife Nawal said: "There wasn’t a body, only a bag full of his body’s shreds and pieces but I had to hug that bag.”
More than 1,500 Palestinian civilians, including 519 children, were killed in Israeli attacks carried out during the latest Gaza conflict, and at least 18,000 homes were destroyed.
Amnesty says it will call on the International Criminal Court to investigate. Israel has said that it will not co-operate with the Commission of Inquiry established by the UN Human Rights Council.
“Failing to allow independent human rights monitors into Gaza smacks of a deliberately orchestrated attempt to cover up violations or hide from international scrutiny," Luther said.
The report comes amid further strife for the people of Gaza. Last week Egypt's army demolished dozens of homes along its border with the Gaza Strip, after the military ordered residents out to make way for a planned buffer zone meant to stop militants and smugglers.
The plan to clear 10,000 residents from some 800 houses over just several days has angered the area's already disgruntled population.
"To throw 10,000 people into the street in a second, this is the biggest threat to national security," said Ayman Mohsen, whose sister left her house located 350 meters from the border. Speaking to The Associated Press via online messages, he said the army told residents to leave on Tuesday within 48 hours, and that houses would be blown up even if people remain inside.
The move to set up the planned 13km buffer zone comes after militants attacked an army checkpoint near Sheikh Zuweyid town last week, killing 31 soldiers. No group has claimed responsibility.