The vice chairman of the Washington Suburban Sanitary Commission resigned yesterday after Montgomery County Executive Douglas M. Duncan threatened to oust him if he did not step down.

Gerald J. Roper told county officials that he would resign rather than submit to a vote by the Montgomery County Council to remove him from his appointed seat on the bi-county water and sewer agency.

For weeks, Duncan (D) and other county leaders have been quietly urging Roper to step aside, and they had set yesterday as a deadline for him to make a decision.

"With the last few weeks the Executive Office, the County Council and I have come to a critical impasse regarding the future of WSSC," Roper said in a statement. "As such, I have been made to endure tactical negative media coverage and intentional misrepresentation of the facts within the public eye. Such tactics are solely designed to compromise my effectiveness."

In the past month, Montgomery's three commissioners -- Jinhee Kim Wilde, Luis Valencia and Roper -- have resigned from the WSSC's six-member board. The resignations came as Duncan worked to prevent the General Assembly from ordering a state takeover of the agency.

The WSSC, which provides water and sewer services to 1.6 million customers in Montgomery and Prince George's counties, has been plagued in recent months by political infighting and allegations of conflicts of interest and mismanagement.

Yesterday, state Senate President Thomas V. Mike Miller Jr. (D-Calvert) applauded Roper's decision, and he urged Jack B. Johnson (D), Duncan's counterpart in Prince George's County, to remove the three commissioners under his control.

"The only thing that will head off state intervention is if County Executive Johnson follows suit," Miller said. "There needs to be a cleaning of house. . . . Either they correct it now or wait for the General Assembly to do so in January."

But Johnson has said repeatedly that he does not plan to seek the resignations of the county's three commissioners, including Chairman Joyce A. Starks. "There has not been a change that I'm aware of," said Jim Keary, a Johnson spokesman.

Members of the Prince George's County Council said their hands are tied and indicated that state intervention was inevitable.

Council member David Harrington (D-Bladensburg) said the council, which has a strained relationship with Johnson, has decided not to "pick a fight with him" over the issue, knowing that "he is not going to budge."

"Does the council focus its energy on telling him these folks are embarrassing, or do we develop policy to make sure it doesn't happen again?" Harrington asked.

Miller said the General Assembly could strip the county executives of their ability to appoint commissioners or it could otherwise restructure the panel.

The WSSC has been in turmoil for much of the year. Last month, the agency's general counsel, Ben Bialek, resigned, comparing the commissioners' leadership style to that of an "army of occupation."

In February, the board voted 4 to 2 to fire General Manager John R. Griffin and his deputy, P. Michael Errico. Bialek ruled the dismissal invalid because the closed-door session was not advertised properly, but in August the board paid the officials $250,000 apiece to step down.

When Wilde resigned last month, she called the board "dysfunctional" and urged the other commissioners to quit.

But in his statement, Roper defended his tenure on the board, saying the drinking water is safe, the commission has a AAA bond rating and minority-owned companies are receiving more contracts. Roper said he plans to establish a "WSSC watch," a group that will "be an advocate for the ratepayers."

David Weaver, a Duncan spokesman, said Duncan is already looking for new commissioners.

Miller said legislators want to see commissioners with broad management and fiscal policy skills. "These are not positions for some ward leader or campaign worker or someone who had made a $50 contribution," Miller said.

Staff writer Ovetta Wiggins contributed to this report.

Gerald J. Roper was under pressure from county leaders.