One reason for the price of rice increasing in recent months is continued demand for biofuels, according to the Nation news portal.The website states that there are a number of factors which have contributed to the hike in prices - but industries seeking environmentally-friendly fuel is likely to be one of the factors that will keep rice fees high in the years to come.World Bank president Robert Zoellick has reportedly warned that food prices may well remain higher than average in the long term due the increasing use of biofuels for low carbon power, as well as the overall strong global demand.The severe weather changes in Vietnam are also said to have had an effect on rice prices.British prime minister Gordon Brown has raised the issue this week - in a letter to the leaders of the Group of Eight nations. He suggested that the government is concerned at the way demand for biofuels has increased global food prices.