Most victims of Myanmar's cyclone remain without emergency food supplies two weeks after the catastrophe, experts said yesterday, with one calling it the worst disaster response in recent memory. Critical supplies are slowly making their way to survivors, but not nearly enough for the up to 2.5 million people who the United Nations says were severely affected by the storm. "I cannot recall a relief operation where, at least the international response, has been subjected to such delays. Where two weeks into it, we don't even have a decent assessment of the numbers affected," said Mark Malloch-Brown, a top official in Britain's Foreign Office. The UN said some 550,000 people now huddled in temporary shelters in the Irrawaddy delta, once an important agricultural zone and now a flooded and ruined region still littered with dead bodies. "People have been migrating outwards from the most affected areas in search of basic necessities," the report said. Those basic needs have gone largely unmet since the storm rammed into Myanmar's southwest and the economic hub Yangon on May 2 and 3. Aid groups say people remain in critical need of food, clean water, shelter and medicine, with the relief effort held up by the ruling junta's reluctance to let experienced rescuers in. "This is dangerously slow. And I would say that unlike the two very recent big disasters -- the tsunami and the Kashmir earthquake -- potentially it has a much greater risk of a second health crisis," Malloch-Brown said. "We are way behind the curve compared to any other international disaster in recent memory," he said here after meeting Thai officials. With no helicopters and a lack of experienced staff on the ground, World Food Programme (WFP) spokesman Marcus Prior said the agency was struggling to reach hungry people. So far, WFP food had reached 50,400 people -- a tiny proportion of up to 750,000 of the survivors facing hunger and starvation. Myanmar says the storm left more than 66,000 people dead or missing. "We have 700 tonnes of rice, high-energy biscuits and beans in the affected areas," Prior told AFP. "We are working to get to the rest of them as quickly as possible." British Prime Minister Gordon Brown said Thursday the United Nations will organise an emergency summit on the disaster, adding that it would be held in Asia.