A federal judge refused yesterday to approve a reduced sentence for a District car insurance agent who admitted defrauding and stealing from at last 80 of her customers, after prosecutors said the agent committed more crimes after striking a plea agreement with them.

Andrea M. Washington admitted in May that she had pretended through 2002 and 2003 to issue car insurance to customers at an insurance agency she ran on Rhode Island Avenue NE, but that she had instead kept their insurance payments and left clients without coverage. She was scheduled for sentencing yesterday under her plea agreement with prosecutors. The agreement was for 12 to 18 months in prison and restitution payments of $23,729, if the court approved.

But U.S. District Judge Richard J. Leon chastised government prosecutors for continuing to endorse a plea agreement that would limit Washington's time in prison despite finding evidence that she engaged in more criminal acts after the agreement was struck. Prosecutors told the judge that they found that Washington defrauded at least 18 new customers by writing phony policies and continued taking payments from 35 previous customers after the May 20 deal.

Leon noted that if the government's allegations proved true, Washington would probably have to do far more time in prison -- as much as 21 to 27 months -- and would probably have to pay back more victims for their losses.

"If the defendant went out and committed these same offenses again, the interests of justice would demand consequences," Leon told Washington, her attorney and prosecutors. "In the interests of justice, I can't proceed with this sentence."

The judge said it was "inconceivable" that prosecutors would give Washington credit for accepting responsibility for her crime if they thought she was committing more crimes. Prosecutors assured Leon that Washington could not victimize anyone else because she had surrendered her District and Maryland insurance licenses and closed her agency office.

The judge wagged his finger at Washington and warned that she would be taken immediately to jail if caught in a criminal act. "Talk carefully to your counsel to make sure you don't come close to crossing the line," Leon said.

Leon ordered the government to produce its new evidence about Washington within 10 days. He scheduled a new sentencing hearing for Sept. 29.

The allegations about Washington writing more phony policies with Progressive Insurance came to light because an attorney who filed a civil suit for Washington's customers discovered new policies initiated by Washington but unpaid. The attorney, David Tompkins, said he alerted the insurance company and U.S. attorney's office in recent weeks.

"As I've said all along, this woman is a master con artist," Tompkins said. "For any person with a conscience, it would be a problem to commit more crimes after you plead guilty."

Prosecutors declined to comment on the case. Washington and her attorney, Michael Fried, declined to comment and left court through a side exit.

Staff writer Clarence Williams contributed to this report.