Pakistan must spend millions of dollars now on rebuilding areas devastated by last summer's floods to avoid massive future loss of life and jobs, a top United Nations disaster official said Tuesday.

Catastrophic monsoon rains that swept through the country in July and August killed thousands, affected 20 million people, destroyed 1.7 million homes and damaged 5.4 million acres of arable land, experts have said.

The floods hit five years after a 7.6-magnitude earthquake in northern Pakistan killed more than 73,000 people and left about 3.5 million homeless.

Officials have previously accused the much-maligned government of failing to properly manage cash funds, hampering relief efforts for flood victims.

The country is at continued risk of natural and man-made disasters and must spend and work now to prevent future damage, Margareta Wahlstrom, UN Special envoy for disaster risk reduction, told journalists in Islamabad.

"Pakistan cannot afford to risk its future and lives of its people by being ill-prepared," said Wahlstrom, during a five-day visit to Pakistan hosted by international aid agency Oxfam.

Political will is needed to halt the disaster spiral, she added.

The UN said that despite some government help, flood victims were relying mostly on their families and communities for help.

"Ultimately, however, it is government's responsibility to protect its people. Government leadership is needed to implement disaster risk reduction strategies and the role of the international community is to support it," a UN statement said.

Last month the UN said the country was still in emergency mode six months after the floods and that $1 billion was still needed -- nearly half of a flood relief appeal launched in September -- mostly to help farmers recover.

The UN put the cost of flood damage at about one third of the government's budget -- up to $10.85 billion -- and said $27 million in spending on disaster risk reduction was needed to reduce losses in future.