Economists expect a four per cent rise in the cost of the UK's weekly shop this year, and food prices are already rising more quickly than those in the rest of Europe.

According to a survey of its members, the National Farmers' Union has forecast a bleak picture of this year's harvest, and wheat in particular has been badly hit.

Bad conditions in the US and Russia, both big exporters of grain, are also contributing to food prices rising globally.

Professor Tim Lang, professor of food policy at City University, told Today presenter Sarah Montague that the rising price of fruit and vegetables "is a disaster for public health".

Lord Haskins of Skidby, a farmer and former chairman of Northern Foods, said the current rise is due to a "temporary blip because of the weather... one must distinguish between the short term problems of ugly looking potatoes in the shops and long term problems of climate change."