Real wages meanwhile fell by more than a third, the UN Relief and Works Agency for Palestine Refugees (UNRWA) said.
Its ree territory.
'Boost to Hamas'
UNRWA spokesman Chris Gunness said of the report in a statement: "These are disturbing trends and the refugees, who make up two-thirds of Gaza's 1.5 million population, were the worst hit."
The unemployment figure, for the second half of 2010, was a slight improvement on the 45.7% jobless rate during the same period in 2009.
Continue reading the main story At the scene Jon DonnisonBBC News
One of the things you notice in Gaza is the tremendous number of people just sitting around apparently with time on their hands - smoking, chatting, shading themselves from the June sun.
This week I met a young man, Rami, a gracrippled by the ban on virtually all exports and the fact that Gazans just don't have the money to spend.
But it was an increase from the first half of 2010, when a temporary building boom boosted jobs.
The UN report says while private businesses have suffered most, the Hamas-run public sector is one of the few areas where there has been economic growth, with the government employing tens of thousands of people.
Mr Gunness said the research had found that since 2007, Hamas had been able to increase public employment by at least one fifth.
"If the aim of the blockade policy was to weaken the Hamas administration, the public employment numbers suggest this has failed," he added.
Israel says the measures against Gaza are necessary to stop weapons smuggling and to put pressure on Hamas, but the UN insists the restrictions amount to collective punishment of Gaza's population.
The Israeli foreign ministry spokesman, Yigal Palmor, says Israel is not against Hamas improving Gaza's economy or running the territory, but wants them to recognise Israel.
Continue reading the main story “Start Quote
Hamas insists on remaining committed only to an all-out war, and that is the systemic explanation of what is happening in Gaza”
Yigal PalmorIsraeli foreign ministry spokesman
"We are totally in favour of Hamas accepting the international community's pre-conditions to become an interlocutor," he told the BBC World Service's World Today programme.
"If they only accepted that - surely that's not too much to ask, to recognise Israel, and to agree to negotiate with Israel - then Hamas would be accepted by Israel too as an interlocutor. And that would certainly immediately alleviate the plight of Gaza.
"But Hamas insists on remaining committed only to an all-out war, and that is the systemic explanation of what is happening in Gaza."
The blockade was eased by Israel last year in response to international pressure, after nine Turkish activists were killed in an Israeli raid on a convoy of aid ships see