Private organizations have increased emergency food aid to the needy by about 20 percent in the past year, and a majority of the groups say they are unable to meet demand, according to a national survey by the Food Research and Action Center.

"The statistical results indicate an increase in demand for food despite the current economic recovery," the center's executive director, Michael R. Lemov, said yesterday. "Absent immediate increases in federal, state and local efforts to alleviate hunger, this will be a long and painful winter for millions of Americans. The recovery has passed many people by."

Lemov said the center's survey also showed that the increased demand for food aid from churches, private food banks, soup kitchens and other providers corresponded to a simultaneous decline in federal food-stamp assistance.

"The decline in food stamps is an administrative and legislative decision," he said at a news conference. "The program has lost $2 billion per year in funding from where it would have been if the eligibility requirements had not been tightened."

The center's survey, which Lemov stressed was unscientific, drew responses from 300 emergency food providers, which serve thousands of households in 36 states and the District of Columbia. The respondents said they were serving 182,000 households in 1984, compared to 151,000 last year.

"There is a paradox between the economic recovery and the increased poverty rate, which finds 47 million people at risk of hunger," Lemov said. "Yet the issue seems to have disappeared. We do not claim this is an exact scientific sample, but we believe we have a valid indicator, a reasonable barometer of the need."

Seventy-one percent of the providers said private charity is unable to meet the demand for emergency help. Yet many reported that state and local government agencies continue to refer to them cases that the governments cannot handle. Sixty-one percent said more than half of the households they serve are families with children.

Other news conference participants from Maryland, New York and Michigan agreed that the need is great.

Montgomery County nutritionist Mary Goodwin said the story of need in the D.C. suburbs "is the same kind of story as Michigan and Nassau County, N.Y."

Goodwin and Jack O'Connell of Nassau County said that although their areas are among the most affluent in the country, the need for emergency food aid has grown dramatically since 1980.

Goodwin said that Montgomery County food pantries in 1980 provided food to 10,000 people but that 20,000 were being served by 1983, "and by the end of 1984 it is expected to triple" to 30,000. She also said that the number of food-stamp applicants had doubled since 1980 but that the rate of refusals tripled.

O'Connell said that in Nassau County, a suburb of New York, more than 30 percent of the food-stamp recipients have been cut from the rolls since 1981, while 75 percent of the eligible people do not get stamps.

He said that despite Nassau's ranking as the highest median-income area in the country, surveys there show 100,000 residents living at or near poverty, and food pantries report a 400 percent increase in demand for emergency food. Another survey, O'Connell said, reported serious hunger and malnutrition among many of Nassau's lower-income people.