The global food crisis intensified on Tuesday as Kazakhstan, one of the world’s biggest wheat exporters halted foreign sales and rice prices shot to a record high after Indonesia stopped its farmers from selling the grain abroad.

In another sign of turmoil, a big food company in Japan, Nihon Shokuhin Kako, said high corn prices had forced it to buy cheaper genetically modified corn for the first time, breaking a social, though not legal, taboo and signalling that opposition to GM foods could weaken in the face of record food prices.