Sir John said: "The security implications should also not be underestimated as food riots are already being reported across the globe.
As well as the riots in Egypt, rising food costs have been blamed for violent unrest in Haiti, Ivory Coast, Cameroon, Mauritania, Mozambique and Senegal. Protests have also occurred in Uzbekistan, Yemen, Bolivia and Indonesia.Read also:Brown urges action on food prices The British prime minister said the problem of hunger was growing for the first time in decade.
This week has seen warnings that soaring global food prices are not a temporary phenomenon, and that there are likely to be more food riots that could cause political instability.
Africa food price 'tsunami' fear
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Riots prompt Ivory Coast tax cuts
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Egyptians hit by rising food prices
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Australia's food bowl lies empty
Q&A: Rising world food prices