Scottish Justice Minister Kenny MacAskill in 2009 handed Lockerbie bomber Abdelbaset al-Megrahi over to Libya on compassionate grounds.
Andrew Fraser, the medical chief for the Scottish prison services, said his research into the case suggested Megrahi had about 3 months to live. He is still alive about a year after his return to Libya.
The decision to release Megrahi gained renewed attention after allegations that embattled British oil company BP was involved in negotiations on a Libyan prisoner transfer.
James Kelly, a Labor lawmaker in the Scottish government, called on Edinburgh to release the full medical reports on Megrahi, the BBC reports. His party said a study in the Journal of Clinical Oncology from 2008 suggests patients with Megrahi's form of cancer can live more than a year after they start chemotherapy, the report adds.
"It's now time for the full facts to come out," he said.
BP, Scottish and British officials have denied any link to the Megrahi release and a Libyan oil deal. U.S. lawmakers incensed over the Gulf of Mexico oil spill are calling for September hearings into the case.
Cardinal Keith O'Brien, the head of the Roman Catholic Church in Scotland, said last week the U.S. hearings smacked of a "culture of vengeance."
Statoil infrastructure brings new barrels