The General Services Administration has received a go-ahead from the White House and Congress to begin trying to buy buildings for federal office space, rather than constructing or leasing them.

GSA hopes to increase the percentage of federal employes working in government-owned space from 53 percent to 80 percent over the next seven years, according to Richard O. Haase, commissioner of GSA's Public Building Service.

Twenty-five years ago, Haase said, 85 percent of federal employes worked in government-owned offices. Since then, the bureaucracy's growth has made massive commercial leasing necessary. Now, he said, leasing costs are escalating "rapidly and uncontrollably."

GSA also is seeking congressional approval to develop a form of trust financing to help it acquire properties, Haase said. GSA would borrow money from the Treasury and pay it back, with interest, from a yet-to-be-determined source. In addition, GSA wants congressional permission to sign contracts allowing it to purchase a property at the end of its lease.

Moreover, GSA plans to explore giving contractors parcels of surplus federal land in exchange for completing a building the government wants to acquire or putting up a new one. Haase said it takes the government seven years to construct a building and the private sector can cut that to less than three years.

With $14.1 million approved by the Office of Management and Budget for its fiscal 1983 budget, GSA has Hill approval to spend just over half of that on its first acquisition target: a 10-year-old office building in downtown Dallas that now houses Labor and Justice department employes. GSA plans to seek about $10 million more in fiscal 1984.

After foreclosing on the Dallas building, the John Hancock Life Insurance Co. offered to sell it to GSA because it was locked into leases with the federal government for most of the building at less than one-third of the going rate for commercial space in downtown Dallas.

GSA Deputy Administrator Ray Kline told Congress that the agency had "an unusually attractive opportunity to purchase the property." Kline said GSA can get the building, valued at $12 million, for $7.2 million; it will then need to do $500,000 worth of work to bring the building up to government fire safety standards. If GSA continued renting through the life of the lease, it would pay $16.5 million.

Locally, a prime target, said one GSA source, is the Transportation Department's headquarters at 7th and D Streets SW. DOT is the only Cabinet department whose headquarters is not in federally owned space. GSA now pays $7.3 million a year in rent for this so-called Nassif building, the highest rental fee for a federal building in the capital region.

Haase refused to target any buildings, saying, "If builder David Nassif knew that we wanted to buy his building, we'd have a lot of trouble negotiating."