ROME — World food prices reached a historic high in January, marking the seventh consecutive month in which a new high has been achieved, according to the Food and Agriculture Organization’s Food Price Index. The index, which is a commodity basket that regularly tracks monthly changes in global food prices, averaged 231 points in January, up 3.4% from December 2010. It was the highest level since the F.A.O. began measuring food prices in 1990. “The new figures clearly show that the upward pressure on food prices is not abating,” said Abdolreza Abbassian, an economist and grains expert with the F.A.O. “These high prices are likely to persist in the months to come. High food prices are of major concern, especially for low-income food deficit countries that may face problems in financing food imports and for poor households that spend a large share of their income on food.” The price index for cereal averaged 245 points in January, up 3% from December and the highest level since July 2008. The increase in January reflected continuing increases in international prices of wheat and maize, amid tightening supplies, while rice supplies fell slightly, the F.A.O. noted.