"Those in power have demonstrated political blindness and a criminal lack of responsibility," Niger's Party for Democracy and Socialism (PNDS) said in its strongest statement on the crisis to date.
Mamadou, who was due to start a tour of some of the worst affected areas on Tuesday, has come under fire at home for failing to publicise the extent of devastating food shortages at an early stage.
Aid workers in Niger have accused donors of failing to respond early to calls for help that began in November, allowing the situation to deteriorate into a humanitarian disaster and dramatically raise the cost of the effort needed to save lives.
But Mamadou's opponents and civic groups say he is also to blame for not taking an early lead in drawing attention to the crisis, saying that he either failed to grasp the seriousness of the situation or was concerned for his country's image.
Images of Niger's starving children have led to a pick up in the flow of international aid over the past two weeks. On Tuesday, USAID said Washington would provide nearly $7 million in additional emergency food assistance.
Mamadou, a former army officer who was re-elected in December, will visit the northern regions of Tahoua on Tuesday and Agadez on Wednesday to assess the crisis in Niger, an arid country on the southern edge of the Sahara desert.
Mamadou made his first trip to affected areas last week when he accompanied visiting Moroccan King Mohammed to the southern town of Maradi, where Morocco has set up a field hospital to help sick women and children.
The PNDS, which announced a contribution of 2 million CFA francs ($3,678) to help the hungry, said Mamadou should not have waited for the visit of a foreign head of state to go and see the situation for himself.
- Reuters - Thomson Reuters Foundation
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