Britain called yesterday for further reforms to UN aid agencies, saying their slow response to disasters had cost lives.

Gareth Thomas, Britain's international development minister, warned that poor nations are likely to face increased pressure as emergencies sparked by war, climate change and high food prices become more frequent and ferocious in coming years.

Yet only one-third of the 42 countries most at risk of conflict or disaster have a UN humanitarian coordinator in place to give on-site leadership during a crisis, he said.

"So in some of the worst disasters there is no one on the ground to lead the international response. The brutal truth is that lack of leadership costs lives," Mr Thomas said in a speech to humanitarian aid experts gathered in Geneva.

In Chad this year, poor coordination among aid agencies had meant drinking water was "allocated unfairly" and people in desperate need had gone thirsty, he said.

"In Georgia, a humanitarian coordinator was eventually appointed but it was quite late. I think it slowed down the response," said Mr Thomas.

The UN's Central Emergency Response Fund, set up nearly three years ago to jump-start relief operations in neglected parts of the world, should be increased to $1 billion a year by 2010, he said.

It now makes about $400 million available a year.