A billion people in Asia are seriously affected by the surging costs of daily staples such as rice and bread, the director general of the Asian Development Bank, Rajat Nag, has said.

"This includes roughly about 600 million people who live on just under a dollar a day, which is the definition of poverty, and another 400 million who are just above that borderline," he said.

Globally, the World Bank last month estimated that 33 countries were threatened with political and social unrest because of the skyrocketing costs of food and energy.

Across Asia, workers made a campaign against high food prices their May Day battle cry last Thursday in marches through cities including the capitals of Indonesia, the Philippines and Thailand.

While the demonstrations were mainly peaceful, concern is growing over the potential for political instability and unrest if high prices persist.

"Once people get hungry they start also getting quite desperate and take desperate measures," Damien Kingsbury of Australia's Deakin University told Agence France-Presse.

India's top farm scientist and architect of the 1960s "Green Revolution," Monkombu Sambasivan Swaminathan, has said India needs a second agricultural revolution to boost food supplies or face huge social turmoil.

Experts blame the high food prices on a confluence of factors, including increased demand from a changing diet in Asia, droughts, the rising use of crops for biofuels, and growing energy and fertilizer costs.