WASHINGTON (AP) -- The 2000 Census cannot be adjusted to make up for an expected undercount of minorities, the Supreme Court said Monday, ruling for taxpayers who challenged the Clinton administration's plan.

The federal census law bars use of statistical methods intended to make the national population count more nearly accurate, the justices said in a divided ruling that could have a major effect on money and votes nationwide.When the census law was amended in 1976, "At no point did a single member of Congress suggest that the amendments would so fundamentally change the manner in which the (Census) Bureau could calculate the population for purposes of apportionment," Justice Sandra Day O'Connor wrote for the court.

O'Connor said "it tests the limits of reason" to suggest that Congress would have been silent in enacting "what would arguably be the single most significant change in the method of conducting the decennial census since its inception."

Adjusting the census likely would have helped Democrats because minorities and inner-city residents, who tend to vote Democratic, made up a large share of the estimated 4 million people missed by the 1990 count.

Republicans oppose adjusting the numbers to make up for that undercount because people who tend to vote Republican also are more likely to voluntarily respond to the census.

Joining O'Connor's decision that adjusting the census figures is unlawful were Chief Justice William H. Rehnquist and Justices Antonin Scalia, Anthony M. Kennedy and Clarence Thomas.

Dissenting were Justices John Paul Stevens, David H. Souter, Ruth Bader Ginsburg and Stephen G. Breyer, who said the federal census law did not bar the government from adjusting the figures.