Britain could have alleviated more suffering if it had reacted quicker to last year's food crisis in the Horn of Africa, the aid spending watchdog has said.
The UK's £200 million intervention achieved "good impact and good value for money", according to a report by the Independent Commission for Aid Impact (ICAI).
But it said that action was delayed because the Department for International Development (DFID) "lacked flexibility" and failed to anticipate adequately the nature of the crisis.
The UK played a central role in the international response last summer as drought led to food shortages affecting 12 million people in Kenya, Ethiopia and Somalia.
The ICAI awarded the British humanitarian work a "green-amber" rating, according to its traffic-light system, meaning that it had performed relatively well but required improvements.
"DFID-supported programmes have benefited some of the most vulnerable people in the worst-affected areas. DFID applied good practices to be accountable to intended beneficiaries," it said.
"Inflexibility in DFID and the humanitarian system, however, meant that action was delayed. Earlier action, especially in Somalia, could have alleviated suffering and, while death rates in Kenya and Ethiopia were not high, both livestock and livelihoods were lost."
The watchdog urged DFID to help develop a better early-warning system for the occurrence of such crises in the future.
"Given the chronic situation in the region, DFID could have been better prepared and we would be disappointed if these challenges were not better addressed in the next response," it said.
The ICAI's chief commissioner, Graham Ward, said: "Overall the UK made a real and positive difference to the lives of millions of women, men and children in dire need in the Horn of Africa. DFID now need to address the recurring crisis in the region and build sustainability and resilience to work towards longer term solutions."