Global food prices could rise further in the short term and keep rising over the longer term as supplies are unlikely to match increased demand, a European Central Bank note said.

The note, prepared for a meeting of European Union finance ministers on Monday and Tuesday, said other factors like protectionist trade policies, speculation and the fall of the US dollar were also boosting food prices.

"In the short term upside risks persist, particularly because futures prices - used as technical assumptions - have proved to be rather unreliable predictors of global food prices," the ECB note said.

People in some European Union countries have been protesting against their loss of purchasing power as the price of basic foodstuffs like bread, milk and potatoes increase. Increase in food prices have already triggered rioting in some Asian countries.

Food and oil price increases have helped to push euro zone inflation to a record high of 3.6 per cent, and the outlook for consumer and wholesale prices will be a central concern at the meeting on Monday of the ECB and euro zone finance ministers.

"Taking a longer term perspective...there are indications that more structural factors may have triggered a re-adjustment of relative prices, suggesting that prices may remain at elevated levels and rise even further going forward," it said.

Food prices have jumped 6 per cent over the last 12 months, mainly on rising demand triggered by rising consumption in China and India, more expensive oil which raises production and transport costs as well as demand from biofuel producers.

The note said that higher supply of food was key to ease the upward pressure on prices.

"The longer term prospects for the supply of agricultural products are presumably the most critical factors. A supply response takes time to evolve and, thus, it seems unlikely, that it would match rising global demand. Prospects are not promising," the note said.

"At the current juncture, a strong acceleration of yield increases seems unlikely and the expansion of arable land is likely to evolve only gradually. On top of this, of course there is always the possibility of weather-related production shocks, which could even become more frequent, should climate change impacts materialise," it said.

It said speculation was also boosting prices as was the depreciation of the US dollar, "which raised demand and reduced the supply response."

Another note on food prices for the ministers' meeting, prepared by junior finance ministers and central bankers, also forecast food could become even more expensive, driven by factors outside Europe.

"Despite the recent fall in (wholesale) prices for some commodities, such as wheat or certain dairy products, the agricultural markets are still tight and the risk of further price increases remains," the junior ministers' note said.

"In the short term, it seems that the growth rates of food prices have reached a peak and are expected to moderate," it said.