Paul Offner, the blunt city administrator who often clashed with other city officials while trying to bring the District's runaway Medicaid budget under control, is resigning to research public policy at Georgetown University.

Offner announced his plans to the D.C. Medical Assistance Administration staff this week and will work the rest of the month, leaving a vacancy at the top of the $838 million program.

Medicaid provides medical and other health-related services to about 130,000 of the city's 523,000 residents and consumes the lion's share of the D.C. Health Department's $1 billion budget.

Before he was hired four years ago, D.C. Medicaid spending was growing by more than 10 percent a year, but in recent years spending growth has been halted. The 2000 budget will decline by $7 million from 1999.

Offner brought about major changes in the program, which has assigned many of its clients to private health maintenance organizations that contract with the city to cover all their health needs.

The contracts were long delayed by challenges from some HMOs but finally took effect last year. He also has been criticized for being too slow to enroll low-income children who became eligible for Medicaid-type coverage under a federal initiative two years ago.

When Mayor Anthony A. Williams (D) took office this year, Offner was at the center of the new administration's effort to expand the Medicaid program to cover most of the city's 80,000 uninsured adult residents.

The proposal was put off until next year by D.C. Council members who feared it might destabilize city hospitals that now care for the uninsured. Williams, who has said he is determined to win an expansion, is likely to try again in the 2001 budget.

Offner "has done an excellent job," D.C. health director Ivan C.A. Walks, who soon will recommend a replacement to Williams, said yesterday. "Under his leadership, we significantly expanded insurance coverage to a lot of citizens in the District. We wish him well."

Another administration official, who asked not to be identified, said Offner had become "radioactive" because of his conflicts with D.C. Council members and officials from Public Benefit Corp., the quasi-independent city agency that operates D.C. General Hospital.