NYPD Commissioner William Bratton Thursday vigorously defended the police crackdown on quality-of-life offenses such as public urination, saying it was vital in keeping serious crime down.

Racial disparities in combating public nuisances were the reality of policing, he said.

"It will continue to be the platform upon which we build," Bratton told a forum on the so-called "broken windows" theory of police work. The concept has been the linchpin in Bratton's quality-of-life strategy of preventing crime by tackling minor problems before they become more serious.

Recently, critics have attacked quality-of-life policing, saying it falls heavily on minorities.

During the forum, Bratton faulted critics of police stop-and-frisk tactics for trying to similarly undermine quality-of-life enforcement. The tactic involves arrests or summonses for low-level offenses.

In later remarks to reporters, Bratton attacked the idea that quality-of-life policing should follow a city's demographic profile.

"The notion that policing is racially proportionate is absurd, completely absurd," Bratton said. He said just because one minority group might make up a certain portion of the city's population doesn't mean that group must be represented by a similar ratio of arrests.

"Sorry, it doesn't work that way," he said. "What is lost on the part of the advocates going forward is the victims, who are also disproportionately minority."

Bratton stressed that police "go where the victims are."

"If those numbers are racially disparate, disproportionate, that is the reality," he said.

But Robert Gangi, director of the Police Reform Advocacy Project, challenged Bratton's argument, saying most of the summons offenses are for victimless crimes such as fare beating, which don't involve complaints from the public.

"There are not 20,000 calls to cops about fare beating," said Gangi, who expressed disappointment at Bratton's stance.

At the same time, Bratton and others at the forum, including Manhattan District Attorney Cyrus Vance, supported the idea that some minor offenses -- such as public urination and lying down in subway cars -- should be handled in civil court or diversion programs.

The forum, sponsored by the Manhattan Institute, a think tank, was aimed at giving context to the crackdown on quality-of-life offenses that has come under fire since Bratton took over in January, his second stint as police commissioner. As top cop under Mayor Rudy Giuliani in 1994, Bratton's campaign against small-time offenders was credited with helping drive serious crimes down.

Bratton reiterated Thursday how stop-and-frisk was linked with quality-of-life actions by police on the street.

"We cannot police effectively without stop, question and frisk and we certainly cannot police at all without quality-of-life policing," Bratton said.