PORTLAND – The proposed transfer of 125 inmates to a privately owned prison in Oklahoma as part of a plan to ease overcrowding in Maine prisons has come under fire from civil rights groups and defense lawyers.

The cost of sending the medium-security prisoners out of state would be about $3 million a year, compared with about $4 million if the state boarded them in Maine’s county jails.

“It’s immediately available, it’s appropriate for that security level and length of incarceration, and it’s also a less expensive option,” said Denise Lord, associate commissioner of the Maine Department of Corrections.

Other temporary measures proposed by the state to house an overflow of 245 prisoners include opening an empty unit at the Charleston Correctional Facility and leasing cell space from Cumberland, York, Lincoln and Sagadahoc county jails, which have excess capacity.

Those opposing out-of-state transfers include the Maine Civil Liberties Union, the Portland branch of the National Association for the Advancement of Colored People, and the Maine Association of Criminal Defense Lawyers.

Critics say sending prisoners far from home would cut off community support and hamper their ability to pursue legal appeals.

“If Maine has a serious criminal justice problem, it shouldn’t be in the business of exporting that problem to other states. We should work together to solve the problem here,” said Zachary Heiden, legal director for the MCLU.

The Oklahoma prison is owned by Tennessee-based Corrections Corporation of America, the nation’s largest private prison company. Maine corrections officials who visited the facility last week described it as clean, safe and well-run, though somewhat lacking in programs compared with Maine facilities.

The company’s extensive experience and economies of scale enable it to house prisoners at lower costs than states can, said Louise Grant, CCA’s vice president of marketing and communication. She said the company also pays less for labor, construction, real estate and heat than many states do.

About half the states pay to have some prisoners housed out of state, according to CCA. Vermont, for example, sent a couple hundred prisoners to CCA in 2004 and now has 500 housed with the company, Grant said.

Maine, with its historically low incarceration rate, is not alone in grappling with a surge in prison population. New Hampshire has about 500 prisoners more than capacity, and Rhode Island’s governor recently declared an emergency to try to deal with that state’s prison overcrowding.

Walter McKee, an attorney who is spokesman for the Maine defense lawyers, questioned the urgency of the Corrections Department’s plan.

“Why are we at this emergency stage in the first place? We’re talking about shipping people 2,000 miles away. Isn’t this something that should have been taken care of a long time ago, before we got into this crisis situation?” McKee said.

Maine’s increase in prison population seems to be linked to a rise in people with shorter sentences being sent to state prison rather than county jails, and to a steady climb in the number of people sentenced for sex and drug crimes.

The emergency plan calls for out-of-state transfers for prisoners who volunteer and those who are from other states but committed crimes in Maine. The department also will review records to see which prisoners have not had regular family contact.

A spending measure before the Legislature’s Appropriations Committee would send prisoners out of state for just eight months, through December, while lawmakers develop a long-term solution to the overcrowding.

Prison population by facility

Maine Correctional Center, Windham

Rated capacity: 522 (male 452, female 70); current population: 689 (555 male, 134 female)

Maine State Prison, Cushing

Rated capacity: 922; current population: 875

Bolduc Correctional Facility, Warren

Rated capacity: 150; current population: 214

Charleston Correctional Facility, Charleston

Rated capacity: 75; current population: 96

Downeast Correctional Facility, Bucks Harbor

Rated capacity: 96; current population: 151

Central Maine Pre-Release, Hallowell

Rated capacity: 50; current population: 55

Total rated capacity: 1,815

Current population: 2,080