Scottish farmers are facing a bleak winter as crop yields have plummeted after a wet summer.

Potatoes and cereal crops have been particularly hard hit, leading to fears that shoppers will be paying more for basics.

Production of almost all crops except oats has fallen.

The first Scottish Government estimates show the wheat crop has been devastated and general cereal production is at its worst since 1994. The 250,000 fewer tonnes of wheat produced this year represents about £40 million to the Scottish economy.

Farmers are reporting potato yields may be down by half after the worst case of blight for 30 years. NFU Scotland vice-president Allan Bowie, who has a cereal and potato farm in Fife, said there would be a "50% yield drop in particular fields" for potatoes.

Such figures, coupled with one of the worst droughts in the US Mid-West for 50 years, and problems for other key global producers including Russia and India, may result in price rises of up to 10% for consumers by the new year.

Barley production is down by 112,000 tonnes, or 6%, to 1.7 million tonnes; wheat production is down 27% to 683,000 tonnes; oilseed rape is down 40,000 tonnes, 26%, to 110,000 tonnes. The oat crop rose 8% to 131,000 tonnes.

The cut in the cereal crop may see 10p added to a loaf and 20p on a packet of breakfast cereal. Falling barley crops may hit the price of whisky.

Economists including Henderson Global Investors were said to have initially estimated prices on a weekly shop could be pushed up 5% by January based on earlier forecasts on crops, but the World Bank has forecast a 10% increase in food prices next year.

Stirling University retail expert Professor Leigh Sparks said: "When you look at what has happened in the UK and then Russia and the US then trading will be much more difficult and there has to be an effect on prices.

"It is difficult to estimate, but you are looking at where all of that fits in terms of food production and the sale of cereal for cattle [feed] which could be an issue."

The Scottish Retail Consortium urged shoppers worried about rising prices not to panic. Supermarkets said shoppers could find better bargains as stores strive to keep custom in a difficult market.