The Federal Emergency Management Agency, plagued by allegations of mismanagement and overspending for the last year, will lay off 200 persons in the next two months or so, Rep. Michael D. Barnes (D-Md.) announced today.

In a statement, Barnes, cochairman of the congressional Federal Government Service Task Force, said that ousted FEMA managers had misused agency funds for their own purposes and shifted program funds to pay salaries not in their budget.

When the House Appropriations Committee capped staff and funding levels in May, the personnel cuts became inevitable, Barnes said.

"It's outrageous that 200 people are being fired because of a laundry list of abuses by Reagan administration officials," he said.

Barnes, who is seeking the Democratic nomination for a Senate seat, said FEMA's current director, Julius W. Beckton Jr., would notify the agency's 2,800 employes by mail today of the impending reductions in force.

They will affect 150 employes in the Washington area headquarters, including some at Olney, Md., before March 31. Another 50 workers at FEMA regional offices will be laid off after that, Barnes said.

Barnes said the cuts were "the bill for the irresponsible behavior" of former FEMA director Louis O. Giuffrida and his deputy, Fred J. Villella.

Giuffrida, a retired brigadier general and longtime associate of Attorney General Edwin Meese III, announced his resignation in July, the day before a House Science and Technology subcommittee probe charged him and Villella with possible perjury and accepting illegal gratuities.

The subcommittee report said Giuffrida had used his influence improperly to win approval of a contract application, spent $5,091 in agency money for plane tickets for his wife and joined in a "deliberate attempt by FEMA management to conceal the overstaffing in management and administration."

The investigation said Villella, who resigned in August 1984, had used $170,000 in agency funds to renovate a training-center dormitory into a private residence for himself, to alter an agency chapel for his daughter's wedding and to pay contract employes for personal services. The two also accepted $2,000 worth of tickets to Republican fund-raisers then billed them to FEMA, the report said.

Earlier, the House Appropriations subcommittee that oversees FEMA refused to let the agency transfer $5.5 million out of emergency planning programs to cover employe salaries.

In its report, the Appropriations panel said that FEMA had indulged in "a pattern and practice of hiring consultants and experts . . . in a manner that implied a willful disregard for the competitive hiring process." Agency officials also committed funds for employes not in its budget, the report said.

"Due to overspending, overstaffing and overindulging by a few, FEMA is now forced to push 200 people over a cliff," Barnes said. "It just isn't right."