The UN is expected to resume aid flights to Burma after charities warned of a disease epidemic of "apocalyptic proportions" due to supplies not getting through.
Agencies have accused the country's ruling junta of delaying crucial relief work needed to help the survivors of last Saturday's cyclone that killed an estimated 100,000 people.
Prime Minister Gordon Brown has echoed their concerns, stating that it was "unacceptable" that restrictions were being put on aid.
At a news conference on Friday, Mr Brown said the Burmese government "must take responsibility" for what is happening.
"We now believe that 100,000 are dead," he said. "It is completely unacceptable that the Burmese government should block the international aid. They should immediately remove the restrictions."
His comments came as members of the Disasters Emergency Committee (DEC) said that they "could do more" if it were not for the opposition from the Burmese ruling junta.
Tim Costello, chief executive of World Vision Australia, said suspicion of foreign aid workers was hampering their work. He warned of an epidemic of "apocalyptic proportions" if aid does not get through.
But he urged donors to continue giving, saying the charities were making a difference.
The DEC appeal by British aid agencies and charities has raised £4 million in two days.
Mr Costello said the Burmese government did not have the capacity to run the relief effort required, adding that the impact of Cyclone Nargis could be worse than the effect of the Asian tsunami on Sri Lanka and Indonesia.
