WASHINGTON -- A federal roadblock has stopped Maryland from counting all prison inmates at their pre-incarceration addresses in order to draw political boundaries.

The Federal Bureau of Prisons has denied the state's request for prior residence information, for residents at the federal prison in Cumberland, Md., because it violates privacy protections, said Chris Burke, a spokesman for the bureau.

An appeal for the addresses has been made to the U.S. Department of Justice, said Andrew Ratner, a representative for the Maryland Department of Planning.

In the meantime, because the Baltimore City charter requires approval of a redistricting map by April 1, the department released revised population figures now that don't take into account the residents of Maryland's federal penitentiary.

"We couldn't wait any longer," Ratner said. "We felt we had to move forward."

If Maryland wins the appeal, redistricting numbers will be adjusted again to account for the former Maryland residents among the roughly 1,500 federal inmates at the Cumberland facility.

Gov. Martin O'Malley signed legislation last April that made Maryland the first state to enact a redistricting law of this type, according to the Prison Policy Initiative, a nonprofit that tracks inmate redistricting legislation.

After the tally of each decennial census, states redraw their governmental districts so that each lawmaker represents an approximately equal number of people. Counting inmates at prison locations has buoyed population figures, giving voters who live near prisons more political clout.

Over the past few years, in anticipation of states redistricting before the 2012 congressional elections, there has been a national push to modify where prisoners are counted. New York and Delaware are implementing similar laws to Maryland this year.

In Maryland, figuring inmates at their last known addresses significantly reduces the populations of counties -- mostly rural -- that are home to state prisons. The adjustment reduces Somerset County's population by more than 10 percent and both Allegany and Washington counties lose about 3 percent with the adjusted numbers.

The population adjustments are particularly important in Somerset, where the county's prison has distorted election districts and inhibited the election of racial minorities, said Meredith Curtis, a spokeswoman for the American Civil Liberties Union of Maryland, which supported the legislation's passage.

The inmate adjustment boosts Baltimore City's population by nearly 6,000 people.

In February, the U.S. Census Bureau reported that Baltimore lost about 30,000 residents -- almost 5 percent of its population -- between 2000 and 2010. Relocating inmates for the purposes of redistricting has narrowed that loss to around 4 percent.

The "No Representation without Population Act" was sponsored by a baker's dozen of Maryland senators and more than 80 delegates.

The adjusted population figures were certified by the secretaries of the MDP, the Department of Public Safety and Correctional Services and the executive director of the Department of Legislative Services.

Capital News Service contributed to this report.