As chief financial officer, Anthony A. Williams fired hundreds of workers, restored order to the District's chaotic finances and won the nickname Tony the Tiger. Later, he swept into the mayor's office on a promise to spread the same ferocious dedication to results and accountability throughout the city's bloated and inept bureaucracy.

But over the past seven years, the Williams administration has been plagued by embarrassing cases of favoritism, bribery and misuse of public funds. Last week, the mayor faced criticism again, this time for tolerating routine violations of city spending laws and widespread use of no-bid contracts.

In an interview Friday, Williams defended his performance, saying waste from contracting and procurement irregularities has diminished dramatically on his watch -- amounting to far less than the $50 million a year cited in news reports -- and that the city has performed well on independent audits.

But he acknowledged that big problems remain, in part because he has not been persistent in weeding out incompetent and unethical city workers.

"Has Tony the Tiger become Tony the Pussycat? . . . I think that is a fair question," Williams said. "And I'm willing to take whatever responsibility I have for maybe being too lenient."

In a city once notorious for cronyism, waste and incompetence, Williams has made significant improvements, according to interviews with more than a dozen political observers, including current and former city officials. The most recent reports are disappointing, they said, but unlikely to tarnish Williams's reputation as a fiscal reformer.

Williams "certainly has eliminated the worst kinds of abuses," said Jamin Raskin, an American University law professor who follows local politics. "He may have just brought the District up to the level of normal municipal abuses."

Still, over the past few years, the Williams administration has drawn criticism for an alleged bribery and leasing scam involving developer Douglas Jemal; the award of a bioterrorism contract to former mayor Sharon Pratt, who has no expertise on that subject; widespread misuse of government-issued purchase cards; and the sale of city property at rock-bottom prices.

Last week, The Washington Post reported that the city's computer office gave a start-up computer consulting company 146 no-bid contracts worth a total of $13 million. Meanwhile, three other city agencies gave nearly $5.4 million to Archie Prioleau, a charming, politically connected and bankrupt businessman who spent some of the money on cars and fancy artwork instead of job-training programs for needy residents. Congress and the D.C. Council have called for investigations.

Former administration officials blame a variety of factors, including Williams's focus on improving city services at the expense of retooling the government's infrastructure. They said Williams has been so intent on getting government working again that he and top aides have spent little time trying to fix the sluggish contracting and procurement system.

In addition, workers in many agencies have not been trained to handle contracts effectively, said Elliott B. Branch, a consultant who spent two years as the District's chief procurement officer. As a result, some agencies get caught in a cycle of crisis. They turn to the same set of contractors to avoid the time-consuming bidding process and use emergency measures -- such as cutting checks without proper authorization -- to deliver services.

"Most of what you're looking at is not people going to Brazil with the money. They're trying to figure out how to get the job done in a complicated system," said former city administrator John A. Koskinen. "The issue four or five years ago was you couldn't get the work done. The grass wasn't cut. The pools weren't open. The suppliers in mental health weren't getting paid. Now, the work's getting done, but the question is: How are we paying for it? Is it being monitored? Can you audit it?"

Some agency heads find ways around cumbersome contracting and hiring rules. Chief Technology Officer Suzanne J. Peck is "an interesting case," Williams said.

Peck, an energetic leader who spent most of her career in the private sector, has brought a government populated by rotary phones into the information age. Her office has rebuilt the city's phone system and is working on a massive computer system to coordinate spending, procurement, personnel and payroll. She also created the city's user-friendly Web sites, which have won national acclaim.

Peck accomplished all this, she told The Post, in part by ordering her contracting officer to stay within the law, but "exploit the hell out of the gray area."

Williams called those comments "at best, inartful, if sincere."

Nonetheless, "she's done a tremendous job," the mayor said. "She's a great example of someone who's trying to get the job done and, overall, is clearly adding value to the taxpayers of the District of Columbia."

Other city workers have more clearly violated the law or demonstrated professional incompetence. But several former administration officials said Williams has been reluctant to prune such people. That reluctance, they said, stems from Williams's 1997 decision as chief financial officer to fire 165 city finance workers he had identified as unworthy. The firings helped Williams gain control of a dysfunctional finance office, but it drew howls of outrage from public employee unions, which endorsed one of his opponents during the 1998 mayoral campaign.

After Williams took office in 1999, those firings and others from the predominantly African American workforce prompted D.C. native Anthony Jenkins to write an opinion piece published in The Post under the headline, "Black Enough: Some People Wonder Whether D.C.'s New Mayor Really Is."

"Who was this man who was using a very blunt instrument to decimate the ranks of District employees? Should people of color be concerned that someone from within their ranks was wielding the ax?" Jenkins wrote.

Two close advisers to Williams at the time said he seemed to grow gun-shy and feared that additional firings would only fuel the perception that, as Williams put it then, "I'm basically going to fire a lot of people . . . and rehire a bunch of white folks."

Last week, Williams rejected that analysis. But he acknowledged that he developed a "more methodical, deliberative approach to change" after his election.

"A lot of my friends said . . . that you should have come in there and done more shooting, and I actually tried that a lot during the first year and it just created a lot of chaos," Williams said. "I think when I was CFO, the way we did those terminations could have been done better. . . . I would never do that again."

Still, Williams said, it is fair to ask whether his administration has truly brought "a new level of accountability" to the city, as promised.

"There should be sanctions across the spectrum where people have done wrong and they've misused government resources intentionally," Williams said. "I don't want to mention any names, but I think there should be. And maybe we'll look to see that there are."

Mayor Anthony A. Williams says contracting and procurement problems have diminished on his watch.