SAN FRANCISCO - Mayor Gavin Newsom showed a "complete and total lack of respect" for the city's police officers by saying a newspaper investigation into use-of-force complaints raised legitimate questions about the handling of problem officers, the head of the city's police union said.

The mayor was "acknowledging there's a problem when there isn't a problem," San Francisco Police Officers Association President Gary Delagnes said Sunday.

Delagnes said the San Francisco Chronicle's series of articles written after a three-year investigation relied on flawed statistical analysis and was the result of biased reporting.

Officers cannot be fairly judged solely by the number of excessive-force complaints against them because many complaints stay on their records even if there are no corroborating witnesses, he said.

"It's just very, very immature and shows a tremendous political naivete on his part to not look deeper into these things and find out what's really going on," Delagnes said.

In an interview published Sunday in the Chronicle, Newsom said he was troubled by reports that about 5 percent of the department's 2,220 officers use considerably more force than their peers, and that in recent years officers used force on blacks in more than 40 percent of the cases.

He pledged to "run roughshod" over the department to install a computerized tracking system by the end of the year to monitor problem officers.

The days of filling handwritten reports are over, said Peter Ragone, a spokesman for Newsom.

"Mayor Newsom, Chief (Heather) Fong, and even Gary Delagnes believe that the current system of tracking use of force is antiquated and needs to be modernized," Ragone said on Sunday.

The mayor also stressed that the majority of officers in the department are doing good work.