Prisoners at a jail in South Carolina are being denied any reading material other than the Bible, according to the American Civil Liberties Union.

The ACLU filed a lawsuit challenging the "unconstitutional" policy at Berkeley County detention centre in Moncks Corner on behalf of monthly journal Prison Legal News last autumn. Last week a request by the US Department of Justice to stand alongside Prison Legal News as a plaintiff in the lawsuit was granted by a federal judge, and the ACLU has now asked a federal judge to block enforcement of a policy which it claims sees the jail's officials "unconstitutionally refusing to allow prisoners to receive any materials that contain staples or pictures of any level of nudity, including beachwear or underwear", effectively banning most books, magazines and newspapers.

Last year's lawsuit quotes an email from a member of staff at the prison to Prison Legal News, which said that "our inmates are only allowed to receive soft back bibles in the mail directly from the publisher. They are not allowed to have magazines, newspapers, or any other type of books". It charges that, since 2008, copies of Prison Legal News and books – including Protecting Your Health and Safety, which explains legal rights to inmates – sent to prisoners at the jail have been returned to sender. There is no library at the Berkeley County detention centre, the ACLU says, so that "prisoners who are incarcerated for extended periods of time have been deprived of access to magazines, newspapers and books – other than the Bible – for months or even years on end".

Officials at the jail responded to the ACLU lawsuit by saying that they only banned material containing staples and nudity. But the new ACLU motion to block this policy points out that legal pads containing staples were being sold at the jail. It claims that the no staples or nudity policy was "adopted post hoc and in response to this Case", and that it "eliminate[s] access to reading material almost as completely as the 'Bible only' rule".

"This is nothing more than an excuse by jail officials to ban books and magazines for no good reason," said David Shapiro, staff attorney with the ACLU national prison project. "There is no justification for denying detainees access to periodicals and in the process cutting them off from the outside world."

"Jail officials are looking for any excuse they can come up with to obscure the fact that they are unconstitutionally censoring materials sent to detainees," added Victoria Middleton, executive director of the ACLU of South Carolina. "And in so doing they are failing to serve the detainees and the taxpayers of South Carolina. Helping prisoners rehabilitate themselves and maintain a connection to the outside world by reading books and magazines is a key part of what should be our larger and fiscally prudent objective of reducing the number of people we lock up by lowering recidivism rates."

Sandy Senn, an attorney for the jail, told the Associated Press that she would contest the new motion.