In an email obtained by the CBC under right-to-information laws and posted online, a director of the Sheriff Services branch told staff not to circulate photos of a sheriff's van involved in a crash last year without her authorization.
Mary Louise Smith told staff in the same email that if they printed the photos they should destroy them, and that sharing the photos or showing them would be a breach of confidentiality.
Lifford said the incident was isolated.
"That's a very disappointing and unfortunate incident," Lifford said Wednesday. "Certainly we don't condone that type of behaviour amongst employees."
Smith could not be reached for comment.
The CBC said one or more inmates were not wearing a seatbelt when the van slid off an icy highway in northern New Brunswick and rolled several times on April 23, 2012.
The government said it won't release its policy on transporting inmates because it is facing a lawsuit from two of them who were involved in the crash.
Lifford said a review of that policy is underway, but wouldn't say when it might be complete or if the findings would be made public.
Liberal justice critic Brian Kenny said the government is not answering questions about the matter.
"Is there going to be any policy coming out on this, and are they withholding any information to the public?" he asked.
Anne Bertrand, the access to information and privacy commissioner, said she only became aware of the matter Wednesday but was concerned by what she heard.
"I am considering looking further into it," she said.