The death toll following the Burmese cyclone disaster could rise to 1.5 million, an aid organisation has warned.

Oxfam said the stricken country faced a public health catastrophe unless clean water and sanitation was quickly provided.

Cyclone Nargis brought death and destruction to the secretive South East Asian country more than a week ago, leaving an estimated 100,000 dead.

But aid organisations fear the slow response by Burmese authorities to the crisis could result in a death toll dwarfing the devastating Boxing Day tsunami which killed 250,000 people.

Sarah Ireland, Oxfam's regional director for East Asia, said: "With the likelihood of 100,000 or more killed in the cyclone there are all the factors for a public health catastrophe which could multiply that death toll by up to 15 times in the coming period.

"In the Boxing Day tsunami, 250,000 lost their lives in the first few hours but we did not see an outbreak of disease because the host governments and the world mobilised a massive aid effort to prevent it happening."

"We have to do the same for the people in Burma. We have the skills and expertise to save lives. We are here to help."

The Burmese authorities are facing increasing pressure to allow supplies and volunteers into the country.

Politicians, senior aid officials and members of the clergy have all condemned the military junta for dragging their feet while tens of thousands suffered.

Aid has slowly started to trickle into the deluged country but humanitarian groups said it was not reaching those desperately in need fast enough.

A Red Cross chartered flight has arrived in the capital Rangoon carrying 35 tonnes of equipment and medical supplies.

But agencies have repeatedly complained that aid is not being distributed quickly enough due to the "frustratingly long" clearance process in the country.

The World Food Programme has confirmed that two planes containing humanitarian supplies had "not been released" by the Burmese authorities after flying into Rangoon.

International Development Secretary Douglas Alexander said a British Government assessment team had been allowed into the country.

He feared the death toll would rise "significantly" from the current 100,000 estimate.

Asked about suggestions that the international community should ignore the regime and "move in" to deliver aid itself, he said: "We are looking at a whole range of possibilities in terms of what we can do.

"But we need to recognise that in terms of effectiveness, getting the aid to the people who most need it, by far the most optimal way for that to happen is with the consent of the regime and the support of the regime."

© Independent Television News Limited 2008. All rights reserved.