WASHINGTON – The Census Bureau is bucking a proposal to change the way it counts prison inmates, saying the change would be expensive and lead to inaccuracies.

The bureau has always counted inmates as residents of the communities where they are imprisoned. That system adds to those communities’ populations, giving them more clout when it comes to laying out legislative districts and divvying up government grants based on population.

However, some big-city congressmen, whose districts typically lose in the deal, want inmates counted as residents of their home towns and cities in the 2010 Census.

Congress told the Census Bureau to study the issue, but the response was not encouraging.

“Our study raises concerns that this change would result in decreased accuracy for a possibly large proportion of millions of individuals confined on census day,” the bureau’s report to Congress said.

The study said it would cost as much as $250 million to determine home addresses for the country’s more than 2 million inmates.

Rural officials who represent areas with prisons praised the report.

But Rep. Jose Serrano, a Democrat from New York City who pushed for the report, condemned it Thursday.

“Instead of providing an overview of how they could make this change in methodology work, the Census Bureau only makes excuses for why they don’t believe it should be done,” Serrano said. “Our nation deserves the very best demographic data. With this report, the census abdicated responsibility for providing that data.”

Serrano contended that inmates should be counted in the communities where they will likely return after their release.

Pennsylvania Republican Rep. Don Sherwood disagreed. He said communities with prisons deserve extra benefits for housing criminals from other areas. Sherwood’s district in northeastern Pennsylvania is home to about 7,000 federal inmates.

Besides, he said, if inmates return home after their release, their home communities will get credit in the following census.