Wholesale prices shot up 1.3 percent in April, the most in 3 1/2 years, the government said yesterday.

Food prices led the way, rising 1.9 percent, their fourth large monthly increase in a row.

The wholesale price index was also driven up by a fluky 31 percent increase in the price of jewelry, caused in part by the rising price of gold.

But after disposing of food and jewelry, prices of goods about to be sold to their final consumers still rose 0.6 percent for the month, an uncomfortable 7.4 percent inflation rate if sustained and compounded for a year.

A spokesman for the Council of Economic Advisers zeroed in on this residual 0.6 percent increase yesterday and said the April figures represent "neither an acceleration nor a deceleration of inflation," which the administration now thinks will be about 7 percent this year.

And traveling with President Carter in the West, Agriculture Secretary Bob Bergland stuck by his earlier estimate that food prices will rise between 6 and 8 percent this year.

But the president himself said in a Claifornia speech that the new numbers "caused me great concern."

Carter is struggling to devise an economic policy that will check inflation and at the same time continue to stimulate the economy to generate new jobs and reduce unemployment.

Inflation fears have become a factor in the committees of Congress now trying to decide whether to cut taxes $25 billion, as Carter has proposed, or some smaller amount, as many legislators think wiser.

Food prices have been rising at an annual rate of more than 20 percent since January, in large part because of rising prices for cattle and hogs. An administration economist said, however, that meat prices are expected to level off soon.

And in any case, most economists think non-food prices are steadier indicators of the true inflation rate than prices for food, which fluctuate erratically.

But John Layng, analyst for the Bureau of Labor Statistics, noted that prices are now increasing steadily for nearly all products, from appliances to automobiles to fuels to industrial equipment. This leaves little room for hope that prices will slow down in the near future.

What is even more disturbing, Layng said, is that inflationary pressures are building up all along the production chain in semi-processed goods such as steel and flour and in raw materials such as iron ore and grain.

Prices of semi-processed goods rose 0.5 percent last month, but would have risen even more were it not for a temporary slowdown in the cost of animal feeds. Flour prices, for example, rose more last month than they did during the first three months of the year combined.

Prices of unprocessed or crude materials rose 2.5 percent in April following a 1.6 percent increase in March, a 3.2 percent rise in February and a 2 percent January increase. It can take a year or longer for these price increases to show up in products that are sold to consumers or to businessmen.

The Labor Department said that its index of finished product prices stood at 191.4 percent of its 1967 average in April. That means that a selection of products that cost $100 in 1967 cost $191.40 last month. The index was 7 percent higher than in April 1977.

Food prices were 8.5 percent higher than a year ago while non-food prices were 5.9 percent higher.

Layng said that the big, 31 percent rise in jewelry prices reflects the rising cost of gold and gems. He said that preliminary evidence suggests that retail jewelry prices are rising even faster.