The world's poorest families are cutting back on food and sending children out to work in order to survive, according to a survey by Save the Children.
The survey, conducted by the charity in India, Nigeria, Pakistan, Peru and Bangladesh, provides a snapshot of the hardship that families are facing in countries already experiencing high rates of malnutrition.
Soaring prices for food have left a third of parents saying that their children did not have enough to eat.
One in six said their children were skipping school to work for food.
The children's charity is calling on the UK to help lead a push to reduce hunger and protect children from food price spikes.
It is urging Prime Minister David Cameron to kick-start this with a "world hunger summit" at the Olympics - a time when world leaders will be in London - to tackle malnutrition.
The report ('A Life Free from Hunger: Tackling Child Malnutrition'), launched today with the help of Myleene Klass, Erin O'Connor and Natasha Kaplinsky.
The charity says that rising food prices and lack of global investment in tackling malnutrition are putting progress on child mortality at risk.
It warns that if no concerted action is taken, half a billion children will grow up physically and mentally stunted over the next 15 years.
The chief executive of Save the Children, Justin Forsyth, said: "Every hour of every day, 300 children die because of malnutrition, often simply because they don't have access to the basic, nutritious foods that we take for granted in rich countries.
"By acting on hunger and malnutrition, world leaders have the chance to change this for millions of children across the world."
Forsyth added that while progress has been made in reducing child deaths, down from 12 million to 7.6 million, this momentum will stall if malnutrition is not tackled.
The charity argues that while malnutrition is the underlying cause of a third of child deaths, it has not received the same high-profile campaigning and investment as other causes of child mortality such as HIV/Aids or malaria.
Commenting on the Save the Children report, International Development Secretary Andrew Mitchell said: "Britain has led the world in tackling food insecurity in the Horn of Africa and will reach 20 million children at risk of malnutrition in the developing world by 2015.
"We are looking further ahead too, supporting scientific research into more sustainable and nutritious crops while addressing the underlying causes of food shortages and malnutrition, from educating farmers and building better roads through to resolving regional conflicts and improving local governments.
"It is absolutely right to focus on the issue of hunger and malnutrition and Britain will continue to urge other countries to match our own efforts in this area."
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