Some five million Zimbabwean rely on food aid, the aid agency says
Acute child malnutrition in parts of Zimbabwe has increased by almost two-thirds compared with last year, aid agency Save the Children says.
In a report, the UK-based agency concluded that some children were "wasting away from lack of food".
It said there was a shortage of 18,000 tonnes of food needed for January and urged world donors to increase aid.
The agency said innocent Zimbabweans should not suffer because of a political crisis out of their control.
"There is no excuse for failing to provide this food," said Lynn Walker, programmes director for Save the Children in Zimbabwe.
The agency said some five million people in Zimbabwe - or about 50% of the country's population - were now in need of food aid.
Zimbabwe's farming sector collapsed after President Robert Mugabe launched a controversial land reform programme more than five years ago.
As well as suffering economic meltdown, Zimbabwe is experiencing a cholera outbreak, fuelled by the collapse of its health, sanitation and water services.
Aid agencies have warned that the disease, which has already claimed more than 1,100 lives, could infect more than 60,000 unless its spread is halted.
President Mugabe has blamed the West for his country's problems.