A sharp jump in gasoline prices led consumer prices 0.5 percent higher in March, the largest monthly increase in more than a year, the Labor Department reported yesterday.

The pickup in inflation last month, measured by the consumer price index, followed advances of 0.3 percent in February and 0.2 percent in January. Although gasoline prices rose sharply last month, other price increases were more moderate.

Some economists said yesterday that the March CPI suggested that the pace of inflation may quicken slightly during the rest of the year.

Consumer prices rose 3.7 percent in the past 12 months and at an annual rate of 4.1 percent during the first three months of the year. The pace so far this year has surpassed the 3.0 percent annual rate in the last three months of 1984.

The CPI stood at 318.8 in March, which means that goods costing $10 in 1967 would have cost $31.88 last month. The CPI-W, another price index used for indexing Social Security, some other federal payments and collective bargaining agreements, was 315.3 in March.

White House spokesman Larry Speakes said the price report showed that "inflation still appears to be well under control. Today's economic news means the Reagan administration has been successful in keeping consumer prices on an even keel."

However, Speakes also said that "prompt, decisive action by Congress in reducing federal spending is essential if we are to maintain the expansion of the U.S. economy."

In a gloomier report, the Commerce Department reported that new orders for manufactured durable goods dropped 2.3 percent in March for the third decline in the last four months. Orders declined sharply in the motor vehicle and aircraft industries and slightly in machinery , Commerce said.

The new-orders report is used to gauge future activity at the nation's factories and so far has reflected the current slowdown in manufacturing and in economic activity in general.

In another report released yesterday, the Labor Department said that real average weekly earnings increased 0.3 percent in March, stemming from a 0.5 percent increase in average hourly earnings and a 0.3 percent increase in average weekly hours.

Economists said that gasoline prices may rise slightly in the short run, although the long-term trend is downward. Gasoline costs rose a seasonally adjusted 3.6 percent last month, following declines of 2.5 percent in February and 1.4 percent in January. However, for the three-month period that ended in March, gasoline prices declined 1.2 percent. Gasoline costs were also 14.4 percent below their peak level in March 1981.

A Labor Department economist said that, because oil prices have been controlled in large part by the Organization of Petroleum Exporting Countries, seasonal adjustment -- the smoothing out of fluctuations based on past patterns of price increases -- has not been easy to determine, resulting in the skewing of some results.

Several factors caused the increase in gasoline prices last month, according to Patrick Jackman, chief of the Labor Department's consumer price index branch. The Soviet Union was not supplying as much petroleum products to Western Europe, and the coal miners' strike in Britain had increased demand for oil, Wood said.

Other prices rose, such as medical-care costs, which jumped 0.8 percent in March following increases of 0.4 percent in February and 0.3 percent in January, the Labor Department said.

However, housing, apparel and other goods and services had smaller increases last month than in the previous month. The index for food and beverages was unchanged after increasing 0.5 percent in February.