Almost a billion people go hungry each day after food price rises pushed 40 million more people around the world into the ranks of the undernourished, the UN food agency reported yesterday.

According to the UN's Food and Agriculture Organisation (FAO), food prices have more than halved from their historic peaks a few months ago, but the cost of basic staples measured by an FAO index is still high: 28% higher on average than two years ago.

That has led to an increase in the number of people unable to afford to eat enough calories to lead a normal, active life. There are now estimated to be 963 million people, 14% of the world's population, going hungry in 2008, up by 40 million from last year.

The FAO's hunger report, the State of Food Insecurity in the World 2008, found that the majority of the hungry live in the developing world, 65% of them in just seven countries: India, China, the Democratic Republic of Congo, Bangladesh, Indonesia, Pakistan and Ethiopia. The worst affected are landless families, particularly households headed by women.

"For millions of people in developing countries, eating the minimum amount of food every day to live an active and healthy life is a distant dream," said the FAO's assistant director general, Hafez Ghanem. "The structural problems of hunger, like the lack of access to land, credit and employment, combined with high food prices remain a dire reality."

Farmers in the developed world have been able to respond to higher prices by raising production, increasing cereal output by 10%. But those in poorer countries have not had the access to the fertiliser, seeds, water and markets necessary to capitalise on the price rises.

Hilary Benn, the environment secretary, will warn tonight that the world faces a "perfect storm" of threats to food security unless leaders agree a deal to tackle rising prices and environmental damage.

In what experts are saying is a significant shift in approach by the UK, Benn will say in a speech to the Fabian Society that there are a range of threats to producing enough food to feed an expected global population of 9 billion people by the middle of this century and he will call for an international agreement along the lines of the Kyoto protocol to tackle global warming.

"Global food production will need to double just to meet demand," Benn is expected to say.

In particular, the UK food system's "dependence on oil will have to change" to use more renewable energy. He also will hint that genetically modified technology may be needed.

At an emergency food summit in Rome in June, world leaders agreed to increase agricultural aid in order to help boost food production in the developing world, but the credit crunch combined with a recent fall in food prices have taken away some of the urgency behind the international effort.

"This sad reality should not be acceptable at the dawn of the 21st century," the FAO's director general, Jacques Diouf, said in a speech to launch the report. "Not enough has been done to reduce hunger and not enough is being done to prevent more people becoming hungry."