Aid agencies have spelled out why they believe the crisis in East Africa would become catastrophic without a big push in international intervention.
The Disasters Emergency Committee (DEC), the umbrella body representing the UK's 14 leading aid agencies, explicitly rejected suggestions they were "crying wolf" over the crisis.
Instead they said they were right to raise the alarm before the current crisis deepened.
The worst drought in over half a century has hit parts of East Africa, affecting more than 10 million people.
DEC has thanked the generosity of the British public after a TV appeal launched on Friday on the BBC and ITV led to £6 million being raised in 24 hours.
Now DEC cited a list of indicators suggesting the situation was far more serious than the frequent seasonal droughts in the region.
They said in some areas the drought is the worst in 60 years with more than 10 million people affected across the Horn of Africa.
Brendan Gormley, chief executive of the DEC, said: "The accusation that aid agencies are crying wolf when we try to raise the alarm early enough to avert a major catastrophe has become wholly predictable. We accept the need to present our evidence and justify our conclusions. All we ask is the opportunity to do so."
"If the public are as generous as we know they can be, if world governments step up and if our members and others rapidly increase their responses then a catastrophe can still be averted. If that is the outcome we accept that part of the price will be that many commentators will ask whether there was ever really a crisis at all."
The DEC members are ActionAid, Age UK, British Red Cross, CAFOD, CARE International UK, Christian Aid, Concern Worldwide, Islamic Relief, Merlin, Oxfam, Plan UK, Save the Children, Tearfund and World Vision.