Homelessness in America is increasing and should be declared a national emergency by President Reagan, the House Government Operations Committee said in a report this week.

The report comes on the heels of a new survey by the National Board Emergency Food and Shelter Program, a coalition of charities funded by Congress, reporting that an estimated 22 percent more people sought public shelter in the past year despite an improving economy.

The committee based its conclusions on eight months of subcommittee hearings headed by Rep. Ted Weiss (D-N.Y.). Its report said that while estimates of the number of homeless range from 300,000 to 3 million, there is no dispute that homelessness has been increasing.

The congressional General Accounting Office, in a report to Weiss' subcommittee, said, "The rates of increase nationwide vary from a Housing and Urban Development Department estimate of 10 percent per year between 1980 and 1983 to a Conference of Mayors estimate of 38 percent for 1983 alone . . . . HUD reported that the number of shelters for the homeless has increased by 66 percent nationally since 1980."

The coalition's survey said estimates by local aid organizations in January and February "suggest that the total homeless population has increased by 22 percent since one year ago." It said that the number of homeless using shelters had increased 16 percent and that the average monthly occupancy rates in public shelters had increased from about 70 percent in January 1984 to 92 percent in December.

Congress appropriated $210 million for food and service aid (except capital expenditures) to the homeless through charitable agencies, the GAO said, but the Federal Emergency Management Agency indicated that it lacks expertise to operate a permanent program and the administration has not sought funds for fiscal 1986.

Weiss called the state of the homeless a "great unrecognized crisis" that requires federal efforts. Committee Republicans dissented, calling homelessness "a tragic situation" but saying that federal programs had not been ineffectual and that more community action was required.

Weiss' investigation concluded that the surge of homelessness resulted from:

* A decline in available low-cost rental housing -- with perhaps as many as 1 million single-room units disappearing during the 1970s.

* Deinstitutionalization of the mentally ill, with the GAO reporting that the population of state mental institutions dropped from 559,000 to 138,000 from 1955 to 1980. The report said the National Institute of Mental Health estimated that up to 50 percent of the homeless may have mental disorders.

* High unemployment rates and cuts in federal assistance programs.

The report said that while a Department of Health and Human Services task force had been set up to coordinate aid to the homeless, "the federal response to the homeless crisis has been disorganized, inadequate and ineffective."

The House committee recommended that the president declare an emergency and direct federal benefit agencies to start programs to identify and help those who need but don't seek it.

Agencies also should be directed to speed up procedures for making surplus food and supplies available and assign priority to aiding the homeless, the report said. It recommended seeking funds for food and shelter for 1986.