Four weeks before Nebraskans are to vote on a proposed ban on the use of affirmative-action preferences by public colleges and other state agencies, the Center for Equal Opportunity has issued a report accusing the University of Nebraska’s law school of engaging in racial discrimination by heavily favoring black and Hispanic applicants.

The report says the advocacy group’s analysis shows that even those black applicants from out of state are more than 20 times as likely to be admitted to the law school, in Lincoln, as white Nebraska residents are. The odds favoring black applicants to the law school over white applicants with the same academic profiles are 442 to 1, the report says.

A news release issued by the center said it also had examined undergraduate admissions at the university but had not found statistical evidence of discrimination. The group said that it had tried to examine the use of affirmative action by the medical school, too, but that the school had refused to provide the necessary data.

Steven L. Willborn, the law school’s dean, dismissed the report today as “a political statement” and said the law school had not provided the center with the sort of data on individual students that would make such an analysis possible. Roger Clegg, the center’s president, acknowledged not getting such data on individual students from the law school but said the information had been routed to his group by another research organization, which he declined to name.

The release of the Nebraska report comes just one week after the center released a report alleging racial discrimination by the law schools of Arizona State University and the University of Arizona. Critics of affirmative action had tried to put a proposal to limit affirmative action before Arizona’s voters this year but failed to gather enough signatures to get the measure on the ballot. —Peter Schmidt