Mohammad Mustafa, an adviser to Mahmoud Abbas, the Palestinian president, highlighted the issue at a donors' conference for Gaza in the Swedish capital, Stockholm, on Friday.
"Given the constraints imposed on us, the situation continues to deteriorate," he said.
"We strongly believe that this man-made humanitarian crisis is political in nature, and thus calls for a political solution," Mustafa said, calling on Israel to open up the border to the Gaza Strip.
He said the most important goal for the conference must be to "end the devastating closure of Gaza and allow the free flow of people, goods and services to and from Gaza".
Jan Egeland, the UN humanitarian chief, announced at the donors conference the European Union has pledged $64 million in humanitarian aid to Palestinians.
Jan Eliasson, Sweden's foreign minister, opened the conference with a Swedish pledge of $5 million for humanitarian aid, along with $3 million to rebuild a power plant that was destroyed earlier this year in an Israeli attack.
Sweden will give another $6 million to a World Bank fund for Gaza, Eliasson said.
"We have to break the viscous circle of violence," Eliasson said. "The feeling of despair must be replaced by hope."
Egeland said the situation in the West Bank deteriorated while the world shifted its focus to the 34-day war between Israel and Hezbollah, calling Gaza a "a ticking time bomb".
"I have travelled to the West Bank for 22 years," Egeland told the conference. "But I never experienced so much disillusionment, frustration, hatred and lack of hope as during my last visit" in July.
Conditions in Gaza worsened after Israel launched a large-scale military offensive in the tiny coastal strip at the end of June.
The operation was in response to a raid in which Hamas-allied fighters who tunnelled under the Gaza-Israel border attacked an army post and captured an Israeli soldier.