The head of the U.N. agency for Palestinian refugees accompanied the first aid convoy in three months to enter the besieged Yarmuk camp in the Syrian capital on Tuesday.
Pierre Krahenbuhl said it was "totally unacceptable" that some 18,000 residents of Yarmouk had not received aid for so long.
Rebel groups inside the camp, the largest in Syria, have been under army siege for more than a year.
More than 200 people have been killed since the siege began, among them dozens who have died of starvation, non-governmental groups say.
"There should be distributions more regularly during the week, not just one day and interrupted again," Krahenbuhl told Agence France-Presse.
The last UNRWA aid delivery was in December, "which from a human point of view is totally unacceptable."
"Certainly there should be no limit to the number of people that we can support in this on a daily basis. This is the thing that has to continue to improve," he said.
Krahenbuhl said he has received "strong messages from the government of their commitment to this happening".
"There has to be a solution to this situation," said Krahenbuhl, who met Syrian Foreign Minister Walid al-Muallem in Damascus on Monday.
He also urged rebel groups "to respect Palestine refugees, to respect civilians and, of course, to not interrupt and interfere with distributions" of aid.
More than 160,000 people -- both Palestinian and Syrian -- lived in Yarmouk before the start of the conflict in Syria that will enter its fifth year on Sunday.
Rebel groups took up positions in the camp more than a year ago, and since June a partial truce has eased the siege to some extent.
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