John Dugard said Israel was largely to blame for turning Gaza into "a prison" and "throwing away the key".
But he also criticised the US, Canada and Europe for withdrawing funds to the Palestinian Authority, run by Hamas militants who do not recognise Israel.
An Israeli official said the statement was unrealistic and over-simplified.
Mr Dugard, UN special rapporteur on Palestinian human rights, said three-quarters of Palestinians in Gaza now depended on food aid - a result, he added, of Israeli military raids, blockades and demolitions.
"I hope that my portrayal... will trouble the consciences of those accustomed to turning a blind eye and a deaf ear to the suffering of the Palestinian people," Mr Dugard told the UN Human Rights Council in Geneva.
The South African lawyer was appointed in 2001.
Palestinian people are punished for having democratically elected a regime unacceptable to Israel, the US and the EU John Dugard
The situation - in the wake of Israel's response to the capture of a soldier by militants from Gaza during a cross-border raid - is worse than at any time during my mandate, Mr Dugard said.
More than 100 civilians have been killed in army raids and bombardments in the Gaza Strip.
"What Israel chooses to describe as collateral damage to the civilian population is in fact indiscriminate killing prohibited by international law," he said.
Mr Dugard also criticised the embargo on funding to the Palestinian Authority since the victory by Hamas early this year.
"Israel violates international law as expounded by the Security Council and the International Court of Justice and goes unpunished," he said.
"But the Palestinian people are punished for having democratically elected a regime unacceptable to Israel, the US and the EU.
"In effect, the Palestinian people have been subjected to economic sanctions - the first time an occupied people has been so treated," he said.
Mr Dugard's brief to investigate Israeli human rights violations against Palestinians has led Israel and its US ally to condemn his reports as one-sided.
The US ambassador to the UN in Geneva cautioned against taking Mr Dugard's view out of context and Israeli envoy Itzhak Levanon dismissed his findings.
"This report is characterised by errors of omission as well as distortions of both fact and law," Mr Levanon said.
He said it ignored what he called the daily experience of Israelis facing Palestinian terrorism.
Mr Dugard is a South African national and won his reputation as a civil rights lawyer during the apartheid era in the 1980s.
Story from BBC NEWS: http://news.bbc.co.uk/go/pr/fr/-/2/hi/middle_east/5382976.stm
Published: 2006/09/26 18:10:11 GMT
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