The UN Food and Agriculture Organisation’s global food price index reached its highest level this year, rising by more than 40 per cent, compared with 9 per cent last year.

"There is a very serious risk that there will be less people able to get access to food because of prices," FAO head Jacques Diouf said.

The cost of imported food for the world’s poorest countries has risen by 25 per cent this year to about $US107 billion the highest on record. Countries facing critical food shortages include 20 African countries as well as Iraq, Afghanistan, Nepal and Pakistan.

Food riots caused by shortages and rising prices have also occurred in Mexico, Morocco, Uzbekistan, Yemen and Senegal.

In its monthly analysis of global food prices, the FAO said there had been an unprecedented "hike in world prices of, not just a selected few, but of nearly all, major food and feed commodities".

Rarely had the world felt such "a widespread and commonly shared concern about food price inflation," the FAO analysis said. In Australia, food prices have increased by 12percent over the past two years, chiefly because of drought and crop shortages linked to global climate change.

Australian Bureau of Statistics data shows prices for bread and eggs have increased by 17 per cent since 2005, vegetables by 33 per cent, honey by 100 per cent, dairy products by 11percent and fruit by 43 per cent.

A recent report by economist John Quiggin for the Australian Conservation Foundation concluded "price shocks similar to those being experienced by Australian consumers during the currently severe drought may start to occur every two to four years, rather than once a decade, unless strong action is taken to reduce global emissions".

Quiggin said some practices proposed as strategies to mitigate the impact of climate change such as growing corn and sugar cane for biofuels and the use of forestry plantations as carbon sinks would inevitably contribute to "upward pressure on food prices".

The impact of biofuels on world food production will be reviewed at a UN conference on food security next year.

It was essential biofuel policies were "coordinated at an international level taking into consideration the objective of fighting hunger," Diouf said.

Higher meat consumption in emerging market nations across Asia are also driving food price increases.

In 1985, China’s average consumption of meat was of 20kg, but per capita meat consumption had now increased to 50kg, Diouf said. This reduced the amount of grain available because 1kg of beef could take as much as 8kg of grain to produce.

The British medical journal The Lancet recently published a study suggesting a 10 per cent cut in global meat consumption by 2050 would reduce greenhouse emissions from agriculture and also improve health for rich and poor nations.

Agricultural experts have also warned global warming will result in shorter growing seasons and smaller crop yields across most of the developing world, affecting the lives of billions of people. A report by the Consultative Group on International Agricultural Research estimates wheat production in India could drop by 50 per cent within 40 years, putting as many as 200 million people at risk of worsening food shortages.

Growing seasons in many parts of Africa will decrease by 20 per cent, with some of the world’s poorest farming communities in east and central Africa including Rwanda, Burundi, Ethiopia and Eritrea among the worst affected.

"The livelihoods of billions of people in developing countries, particularly those in the tropics, will be severely challenged as crop yields decline due to shorter growing seasons," International Rice Research Institute director Dr Robert Zeigler said.

The FAO said soaring petroleum prices had contributed to price increases for agricultural crops by raising farm production costs and boosting demand for biofuels.

"The combination of high petroleum prices and the desire to address environmental issues is currently at the forefront of the rapid expansion of the biofuel sector: this is likely to boost demand for feedstocks, most notably, sugar, maize, rapeseed, soybean, palm oil and other oil crops as well as wheat for many more years to come."

According to the FAO, the amount of corn used for biofuel production in the US will double to 110 million tonnes by 2016. In Europe, the amount of wheat devoted to biofuel will rise twelvefold to 18 million tonnes by the same date.

Earlier this year, Jean Ziegler, the UN’s Special Rapporteur on the Right to Food, denounced biofuels as "a crime against humanity" and called for a five-year moratorium on their production.