A humanitarian fund should be set up to give the UN cash on demand to tackle crises like Niger, the International Development Secretary has said.
Aid finally began to arrive in Niger at the weekend
Hilary Benn says the current system of reacting to emergencies "doesn't work".
He was speaking as a flight organised by Save the Children, with 41 tons of emergency feeding supplies on board, set off for drought-hit Niger.
Oxfam's Phil Bloomer contrasted the situation with "substantial and swift" funding always found for Iraq.
Mr Bloomer backed calls for a $1bn emergency fund, saying it could have prevented the famine, despite the slowness of the international community to respond to appeals.
The aid travelling out to Niger is from the Department for International Development, part of £3m pledged to help the estimated 3.6m people in need.
Mr Benn said the UK had been "one of the first countries to respond" to the UN's flash appeal, which sets the alarm bells ringing of an impending crisis in May.
"It was only in the middle of May that people really became clear about the scale of the crisis," he told BBC Radio 4's Today programme.
"Does the international system work properly in these terrible tragedies? The answer is, it doesn't and that's why in December last year I made some proposals for fundamental change.
"I'm afraid the crisis we are now seeing unfolding in Niger is a really good reason why we have to do better in the future."
The current system involves the UN identifying the problem, and its different agencies and non-governmental organisations going round asking for donations of food or cash.
Mr Benn said this was just like fire-fighting, with a situation occurring and people getting on the phone to various donors asking for a fire engine and fire-fighters.
Mr Bloomer, Oxfam's campaigns director, said an emergency fund would enable the UN "to act swiftly" to avert terrible crises - but the political will was needed to set it up.
"The British Government does respond more effectively than others to the humanitarian crises around the world and is less affected by political expediency," he told Today.
"Nevertheless, the British Government has also made sure that the funding for Iraq say, is both substantial and swift, but whereas in cases such as these we are still looking for a much swifter and more effective action."
The Save the Children flight from Ostend to the Niger capital Niamey will be carrying specialist food and equipment to support one month of feeding for severely malnourished children and those recovering from malnutrition.
A World Food Programme plane from Rome will be carrying 80 tons of high-nutrition biscuits and logistical equipment.
Agencies including the Red Cross and Medecins Sans Frontieres have already started feeding some children, but many people have to be turned back from feeding centres because there is not enough aid for all.
On Saturday the United Nations' relief chief said aid had finally begun to arrive in Niger, but only after graphic pictures of starving children were broadcast last week.
Appeals in November, March and May had failed to generate enough aid.
Experts are warning the crisis could get worse before it gets better.
The combination of locust damage and drought is also affecting Mauritania, Mali and Burkina Faso.