Prices charged by producers rose 0.8 percent in December, bringing the inflation rate at the wholesale level to 12.5 percent for all of 1979 -- the steepest rise in five years -- the government reported yesterday.

The increase, while still high by historical standards, marked a slowdown from the 1.3 percent jump recorded in November and was the smallest monthly rise since June.

However, the improvement was concentrated entirely in food prices, reflecting earlier declines in farm prices. Prices of non-food items soared 1.2 percent in December up from an 0.8 percent increase the previous month.

In all, the index provided little, if any, hope that inflation might abate soon. Retail prices whose behavior often parallels those at the wholesale level, have been rising at a 13.1 percent annual rate.

John Laying, prices specialist at the Bureau of Labor Statistics, which compiles the price report, conceded he saw few bright spots in yesterday's figures. Laying said there were "not a lot of places" that pointed to a slowdown.

The 12.5 percent increase for the year was the largest since 1974, just before the last recession, when wholesale prices rose a sharp 18.3 percent. In both years, sharply rising energy prices were a major factor.

Yesterday's figures constituted grim news for the Carter administration, which had hoped to see some slowdown in inflation by the end of last year. This year, economists are forecasting an inflation rate of 9 to 10 percent.

The retail price index for December, scheduled to be published January 25, is expected to show a jump of between 1 percent and 1.5 percent for December, most likely bringing the overall inflation rate for 1979 to 13 percent or higher.

By comparison, retail prices rose 9 percent in 1978, while wholesale prices jumped 9.2 percent. Although producer prices influence retail prices heavily, there is no dollar-for-dollar relationship.

The improvement in producer food prices -- those charged for goods ready for sale by supermarkets -- resulted in a modest 0.1 percent decline. By contrast, these prices soared 2.6 percent in November.

The major declines last month were in veal and beef prices, which fell 4.3 percent, and in prices of processed poultry and fresh and dried vegetables. All had risen sharply in November.

At the same time, however, prices of non-food items rose steeply in December, reflecting high prices for jewelry, housewares, energy and auto prices. The rise in jewelry prices stemmed from speculation in the gold market.

Prices of intermediate goods -- not quite ready for shipment to retail outlets -- leaped 1.2 percent in December, following an 0.9 percent jump in November. And prices of crude materials rose 1.1 percent after a 2 percent rise in November.

Yesterday's report left the overall producer price index at 227.8 percent of its 1967 average, meaning it took $227.80 to buy the same goods at wholesale that cost $100 just 13 years ago.