As the debate over the extent of the problem of homelessness flared on Capitol Hill yesterday, D.C. officials moved to help the homeless in the face of plummeting temperatures.

David E. Rivers, director of the city's Department of Human Services, announced an effort to protect street people from hypothermia. Department workers and volunteers, he said, will begin patrolling locations frequented by homeless persons to provide food, blankets and transportation to shelters. An unidentified man who was found lying in a downtown park Monday died of hypothermia.

Meanwhile, during a House subcommittee hearing, Rep. Bruce F. Vento (D-Minn.) said that a controversial U.S. Department of Housing and Urban Development report on homelessness should be consigned to the "ash heap of history." However, subcommittee chairman Henry B. Gonzalez (D-Tex.) refused to call its authors before the panel to answer allegations of perjury and falsifying statistics.

The allegations, raised by homeless people's advocate Mitch Snyder after the HUD report was issued in May 1984, center on whether the report's estimate of 250,000 to 350,000 homeless persons nationally was intentionally low.

Snyder, leader of the Community for Creative Non-Violence, said he was "begging" the housing and community development subcommittee chairman to compel HUD officials to answer the charges that they played down the magnitude of the homeless problem. CCNV says there are 2 million homeless.

"As long as people go to bed at night thinking there are only a quarter of a million people without homes, because their government told them so, that report is killing people," Snyder said.

Gonzalez agreed the report "has been used as an argument to do nothing" on the national level for the homeless. However, he said he could not subpoena HUD officials without the consent of his colleagues on the panel, and doubted such an inquiry would aid the cause of the homeless.

"If we compel [the project director of the report] to come . . . , find her guilty, string her up and burn her in oil, what have we done?" he said.

Jayne Gallagher, HUD deputy assistant secretary for public affairs, said the agency had "no comment" on the charges and added that "the committee itself has all the facts."

In addition to CCNV's conflict with the federal government over the national estimate, the advocacy group is fighting the U.S. Department of Health and Human Services' plan to close a CCNV shelter at 425 Second St. NW.

CCNV officials said 640 people spent Tuesday night at the Second Street shelter, while a D.C. Coalition for the Homeless spokesman said the homeless rolls at its Anacostia men's shelter rose to 411.

Key testimony at the subcommittee hearing came from sociologists Richard Appelbaum and Eugene Ericksen, who outlined what they said were defects in the methodology used by HUD in determining the numbers of homeless. In many cases, they said, HUD based its conclusions on insufficient information.