The Reagan administration's proposal to discontinue fire safety and building technology research at the National Bureau of Standards drew a cross section of warnings yesterday that it would cost up to 600 jobs at the Gaithersburg facility and cripple the nation's programs for fire prevention and building code research.

Testifying before the House subcommittee on science, research and technology, Rep. Michael D. Barnes (D-Md.), whose district includes the federal agency, said elimination of NBS's Center for Fire Research and Center for Building Technology would make the United States "the only nation in the world without a national fire and building research program."

And, he argued, "no one else can do this work, and it is vitally important that the work continue."

NBS budget cuts amounting to more than $19 million have been proposed by the Reagan administration as part of its determination to transfer certain federal functions to the private sector. They would mean reductions in force for an estimated 300 to 400 full-time and 200 part-time employes at the agency.

An NBS spokesman said yesterday that once the two research centers were closed and computer science research trimmed at the bureau by 70 percent, the administration would expect that firms and state and local governments would take over with their own research programs.

But firms neither can nor want to take the government's place in research, petroleum refiners, architectural, building and engineering groups and the U.S. Chamber of Commerce said yesterday in opposing the budget cuts.

"The innovative work done by both these centers can make important contributions to meeting the technological challenges" in the construction industry, said John S. Bush, chairman of the chamber's construction action council. "They provide unique research capabilities and perspectives which cannot be duplicated in the private sector."

Bush and other witnesses particularly cited NBS's research in housing insulation problems, improved design and construction procedures, bridge construction, fabric flammability, combustible materials and fire protection methods in high-rise buildings.

In addition, the executive director of the Association of Petroleum Re-refiners, James A. McBain, complained that the Reagan budget contains no funds to complete a current NBS research program on recycled oil. NBS, he said, is in the final phases of a three-year-old study and needs $800,000 to complete it.

"Without completion of the verification studies now under way, past research and developed tests will not be proven and all past funding, almost $8.5 million, will have been wasted," McBain said.