The D.C. Coalition for the Homeless, reacting to allegations of financial improprieties and physical abuse of residents, defended the operation of its Anacostia shelter yesterday while a rival shelter group blasted the coalition and the federal government for their handling of the homeless problem.

Elisabeth Huguenin, the coalition's president, said at a news conference that the coalition has fired an employe arrested last week on a charge of beating a shelter resident with a baseball bat, and she called it an "isolated event."

Huguenin said that top coalition officials had not received information about other alleged assaults on shelter residents but that the group has ordered an investigation in the aftermath of news reports that police are aware of a series of reported assaults on shelter residents by staff members.

"I don't know of any other incidents," Huguenin said.

Mitch Snyder, the spokesman for a rival homeless advocacy group that for months has been involved in bitter dispute with the coalition over who should care for the homeless, told reporters at a separate news conference yesterday that the allegations of assaults and misuse of federal funds prove that the coalition is incapable of managing the homeless problem.

Snyder, a leader of the Community for Creative Non-Violence, also expressed concern that an agreement reached with the federal government last month to resolve a long-running controversy over his group's operation of a federally owned shelter at 425 Second St. NW may be in jeopardy.

He said the agreement's requirement that ownership of the Second Street building be transferred to the city has drawn opposition from Rep. Jack Brooks (D-Tex.), chairman of a House committee that oversees government property. According to Snyder, Brooks wants the federal government to lease the building to the city rather than to transfer ownership, and CCNV and the city agree with Brooks.

Brooks could not be reached for comment yesterday. An aide to Brooks said yesterday that she believes that all Brooks wants is for federal officials to follow standard procedures for the disposition of federal property.

Snyder said he plans to give the Reagan administration one week to work out the details on the building's transfer because any further delays might prevent the shelter from being renovated in time for next winter.

The agreement, announced with much fanfare last month, provides for the federal government to give Snyder's group $5 million to renovate the shelter. It followed a month-long hunger strike by Snyder and others.

"If we have to fast again, we will," Snyder said yesterday.

With regard to the coalition, Snyder said he will ask federal officials today to block the group immediately from spending the remainder -- about $2 million -- of a $3.7 million federal grant given to the coalition last fall.

Informed of Snyder's comments, Huguenin said the coalition is fully capable of caring for the homeless. "I don't know why he said it," said Huguenin, who earlier yesterday had said the two groups were narrowing their differences. "It really saddens me that he said that."

The federal funds were given to the coalition, a private advocacy group for the homeless, last fall to establish an emergency shelter for the homeless in Anacostia as an alternative to the Second Street shelter run by Snyder's group. The federal government had called the CCNV shelter poorly run and a decrepit firetrap and was trying to shut it down.

Allegations that thousands of dollars of federal funds may have been misspent or improperly diverted to coalition officials and others are the subject of an investigation being conducted by D.C. police and the FBI, according to city and other law enforcement officials.

Investigators are looking into the coalition's efforts to purchase shelter facilities throughout the city, as well as a $1,000 payment from a contractor doing business with the coalition to Dennis Bethea, a former coalition board member and former chief of the D.C. Office of Emergency Shelter and Support Services. Bethea has characterized the payment as a loan and has denied any wrongdoing.

Yesterday, Lawrence Guyot, the coalition's treasurer and an official with the D.C. Department of Human Services, said police internal affairs investigators are attempting to show that he acted improperly in handling real estate transactions for the coalition.

Police are investigating a real estate deal negotiated primarily by Guyot in which the coalition paid $21,000 to District police officer Vernell R. Tanner. The money was an advance payment for rent to operate a coalition shelter in a Northwest building that Tanner intended to purchase but did not own. "There's an attempt by the [police] to make this look underhanded between Mr. Tanner and myself," Guyot said. "I've got nothing to hide."

Tanner, while declining to discuss specifics, has said that he has done nothing illegal and that he will repay the coalition when agreement is reached on money he said is owed to him by the coalition.

"A mess has been created," Snyder said of the coalition's management of the federal funds and the Anacostia shelter. "The taxpayers' money is being squandered."

Huguenin, who acknowledged the investigation, said, "If there is any impropriety on the part of any individual or individuals associated in any way with the coalition, these individuals acted without authorization from the coalition . . . . "

Huguenin said the coalition, which has made the safety of shelter residents a priority, probably will change its employe application forms to include a question about criminal records. Otis M. Bridges, the dismissed employe charged with the assault, had a criminal record, but Huguenin said the coalition had been unaware of it.