The salt content of most processed foods has not changed significantly in the last year, despite government efforts to get manufacturers to cut sodium voluntarily, a consumer group charged yesterday.

A survey of 100 commonly eaten processed foods, conducted by the Center for Science in the Public Interest, found that only a dozen had less salt in 1984 than in 1983, and 10 foods had more salt. The other 78 foods showed no change, the center reported.

In a larger survey of 125 "product lines," ranging from Jell-O's array of puddings to Swanson's frozen dinners, CSPI found decreased sodium in 26 lines and increased sodium in 21.

CSPI officials said the survey demonstrates the need for stronger federal action to reduce sodium in processed foods. Excessive consumption of sodium has been linked to high blood pressure, which afflicts more than 60 million Americans.

Health specialists recommend limiting sodium intake to 1,100-3,300 milligrams a day for adults, depending on the person's size and the amount of food normally eaten.

"Most of the sodium in the average American's diet comes from processed foods, and most corporate chefs show no signs of changing their cooking habits to protect the public's health," said CSPI nutrition director Bonnie Liebman.

Consumer activists are pressing for mandatory labeling of sodium content and restrictions on the amount of salt permitted in processed foods.

The Food and Drug Administration deferred such action in 1982, saying it expected that the food industry would reduce salt content voluntarily.

But Bruce Silverglade, CSPI's legal director, said the group's survey shows that "manufacturers have not reduced the salt content of their products sufficiently to justify any further delay . . . . It is high time that FDA set mandatory limits on the salt content of processed foods."

The center declined to release its list of 100 commonly eaten foods, saying it wanted to prevent companies from distorting its index by modifying the sodium content of those items alone.

But it released the results of its "product line" survey and praised some manufacturers for significant reductions in sodium.

Among them was Pepperidge Farm, which reduced the sodium content of its English muffins by 34 percent, to 214 milligrams per serving.

The salt content of Pepperidge Farm muffins is now about the same as Thomas' English muffins, according to the survey.

Banquet reduced the average salt content of its frozen dinners by 27 percent, to 1,565 milligrams per serving. Kraft cut sodium in its processed cheese spreads by an average 28 percent, to 456 milligrams. And Mrs. Paul's trimmed 21 percent of the salt from its frozen fish line, to 799 milligrams.

Companies that increased salt content included Pillsbury, which raised the sodium content of its Figurines diet bars an average of 58 percent, to 217 milligrams a serving. Green Giant's frozen pouch entrees went up an average of 33 percent in sodium, to 961 milligrams. And General Mills boosted the sodium in Tuna Helper by 22 percent, to 882 milligrams.