Hundreds of thousands of people are still living in makeshift homes 18 months after Cyclone Nargis killed at least 140,000 people in Myanmar, the UN has said.

International donors have pledged a fresh $88m for 17,800 new houses, 40 new schools and livelihood programmes for one million people.

But Bishow Parajuli, the UN resident and humanitarian co-ordinator in Myanmar, said on Wednesday that the amount falls far short of what is needed.

"What is reflected here is not what is needed. It is a much-reduced version of what may be possible to do between now and July," he said.

The pledge falls short of the $103m sought for the period until July by the UN and the Association of Southeast Asian Nations regional grouping that includes Myanmar.

The UN says 178,000 families need help with shelter and the shortfall in funds will leave about 100,000 families without a proper home.

Most of those families are living in makeshift homes covered with threadbare tarpaulins distributed in the early phase of the relief effort, according to aid workers.

Srinivasa Popuri, the leader of a shelter aid group in Myanmar, told the Reuters news agency that "the materials have gone through two monsoons and they won't last another season".

Cyclone Nargis swept through Myanmar's Irrawaddy delta in May 2008, flattening villages, destroying 450,000 houses, killing 140,000 people and leaving 2.4 million destitute.