Consumer prices shot up another 1.4 percent in March, sustaining an 18.2 percent inflation rate for the third month in a row, the government reported yesterday.

The overall increase came despite a marked deceleration in energy prices, meaning inflation worsened in other sectors. Supermarket prices rebounded after two months of decline.

In a separate report, the government said that consumer prices in the Washington area rose 3 percent in February and March combined, more than nationally and the most in three years.

The Department of Health, Education and Welfare announced that, based on the national price figures, Social Security and Supplemental Security Income benefits will automatically increase 14.3 percent, beginning with checks sent out in July.

But the rising prices continuedd to cut into workers' purchasing power. The Labor Department's hourly earnings index, adjusted for inflation, fell 0.3 percent. It now stands 5.1 percent below a year ago.

The White House conceded yesterday that the so-called underlying inflation rate -- the rate expected to persist after rising energy and mortgage costs work through the economy -- has jumped to 12.7 percent, from 8 percent.

R. Robert Russell, director of President Carter's Council on Wage and Price stability, told Congress that "the real disconcerting thing is what is happening to the underlying rate of inflation."

Russell said even if consumer prices moderate substantially later this year, as Carter has predicted, the underlying inflation rate will still have risen significantly, heightening pressure for wage increases.

The administration's fear is that the continuing price increases will "spill over" into rising wage demands and well trapping the economy in a classic wage-price spiral. The current guidelines program is aimed at headng that off.

Yesterday's figures were announced as voters began going to the polls in the crucial Pennsylvania primary, where Carter was in a contest with Sen. Edward M. Kennedy (D-Mass.), largely over pocketbook issues.

Kennedy, at home waiting for the primary results, issued a statement urging voters to "send a messagee to the Rose Garden" that "enough is enough," and said it's time "we had a president who can stop inflation and bring our economy back to health."

For Carter's side, presidential press secretary Jody Powell asserted that mortgage interest rates -- one of the main factors in the recent inflation -- "have already begun to top off" since March. He predicted "significant" price relief by autumn.

The 18.2 percent annual inflation rate recorded over the quarter -- 18.1 percent after statistical rounding -- was the most for any such period since early 1951, during the Korean war.

The consumer price index now stands at 239.8 percent of its 1967 average, meaning it took $239.80 to buy the same goods and services in March that retailed for $100 just 13 years ago. The index is 14.7 percent above a year ago.

The rebound in food prices ended two months of calm in which grocery prices declines. The March increases came mainly in beef, sugar and vegetable prices, and stemmed primarily from incresed distribution and packing costs.

Russell said the administration still expects food prices to rise only 7 to 11 percent this year, with monthly increases ranging between 0.5 and 1 percentage-point until well into the summer.

However, Howard W Hjort, the Agriculture Department's chief economist, told a news conference that "by the time the president's" anti-inflation "program is successful, food prices will start taking up the slack."

Hjort said he expected food prices to begin rising more rapidly than the overall inflation rate by the end of this year. He said farm prices have remained relatively low and would "have to catch up."

Here is a rundown on yesterday's price report:

Food: Grocery prices nationally jumped 1.1 percent in March, following declines of 0.4 percent and 0.2 percent in February and January. Apart from beef, sugar and vegetables, most supermarket prices rose more moderately than in February.

Energy: Energy prices slowed substantially as the economy began to recover from the impact of December's crude-oil price ncreases. Energy prices rose 3 percent in March, down from a 5.1 percent boost in February.

Gasoline prices jumped by 3.9 percent.

Housing: Overall housing costs leaped 1.6 percent in March, following increases of 1.4 percent on each of the two previous months, but the news -- in the fact of the mounting housing slump -- was mixed.

Although home mortgage interest rates continued to rise sharply, house prices edged up only 0.4 percent, their second such moderate increase in two months. However, the cost of maintenance and repairs climbed 1.7 percent.

Other Items: Apparel prices jumped 2 percent, mainly reflecting higher prices for spring clothing, but prices on transportation and medical care rose more slowly than in February, albeit at rapid rates.

Transportation costs in March jumped 1.7 percent, down from 2.8 percent in February, mainly because of a reduction in energey-price increases. pPrices for medical services rose 0.9 percent, compared with 1.5 percent in February.

Russell told the congressional Joint Economic Committee the administration expects consumer prices to rise by between 1.2 percent and 1.4 percent a month "until early summer, fater which we will have a marked decrease" in inflation.

The figures came as separately, the Commerce Department reported that new factory orders for durable goods -- a key indicator of economic activity -- fell 3.2 percent in March, adding to earlier signs that the recession begun.