Prince George's County Council member Peter A. Shapiro (D-Brentwood) announced yesterday that he will resign from the council next month to take a full-time job at the University of Maryland, his alma mater.

Shapiro, 41, has served six years on the nine-member council and is one of its most senior members.

His resignation, effective July 16, comes more than two years before the end of his second term. Term limits would have prevented him from running for reelection.

"It's a tremendous opportunity that I couldn't pass up," said Shapiro, who will work in the university's School of Public Policy to improve the relationship between the university and communities in Prince George's County. "The time is right. . . . I set some pretty clear goals on what I wanted to accomplish [on the council], and I feel like I have been successful."

Shapiro, who relinquished his role as council chairman in January, said his resignation is partly due to frustration over moving out of a leadership position and discomfort over the council's approach to dealing with County Executive Jack B. Johnson (D).

During the General Assembly session last year, Johnson pushed hard to secure passage of a bill allowing him to oust the county's five representatives to the powerful Maryland-National Capital Park and Planning Commission and replace them with his own appointees. The maneuver angered more than a few council members, who felt Johnson was trying to exclude them.

Shapiro, who was council chairman at the time, chose not to criticize the county executive. That decision upset many of his colleagues, who thought they needed to assert their authority. When his chairmanship ended, his political influence diminished.

"I'm the first one to admit that it was a difficult transition personally," Shapiro said. "As you make life decisions, you take everything into account. . . . It's been difficult for all of us. I have a lot of respect for and a good relationship with my colleagues."

Shapiro said he will return to the University of Maryland, the school from which he received an undergraduate degree in 1994, as a senior fellow at the James MacGregor Burns Academy of Leadership, a staff position he held before joining the council.

His announcement yesterday surprised many people in county political circles. Speculation swirled about who will fill the vacancy and how the replacement will affect the makeup of the council, whose members have clashed in recent months with Johnson and Andre J. Hornsby, the county's schools chief.

The County Council is scheduled to decide July 20 when to hold a special election to fill Shapiro's seat.

Shapiro has been a central figure on the council, having served two consecutive years as chairman and having led committees that dealt with planning, zoning, economic development, transportation and environmental issues. He has pushed for a plan to transform 286 acres along the Route 1 corridor into a neighborhood of studios, galleries and restaurants in his district, which includes the towns of Hyattsville, Brentwood, North Brentwood and Mount Rainier.

He also is a board member of the Metropolitan Washington Council of Governments.

Tony Knotts (D-Temple Hills), who replaced Shapiro as council chairman in January, said in a statement: "Mr. Shapiro's departure will bring about a temporary void which will need to be filled. However, his legacy is in his mentorship and his tutelage for me and others with whom he has left a positive impact."

Shapiro, a former member of the Brentwood town council, brought to the County Council more than a decade of experience as a political and community organizer, having worked with Citizen Action, Clean Water Action, the Institute for Social Justice and the National Rainbow Coalition.

Shapiro, who sports a goatee and a diamond-studded earring, was seen as a hip, progressive addition to the council when he joined in 1998.

"He evolved from a populist who wanted to change the system into a great compromiser," said Wayne Clarke, a lobbyist for the council. "And I think he got stuck in the position as the great compromiser.

"This council bases its decisions strictly on principle, and oftentimes there is no room for compromise when you make a decision on principle."