The prisoner is understood to be Jason Sutherland, who is serving a life sentence at HMP Greenock for murder, and is due to be released shortly because he is terminally ill.

Kenny MacAskill, the Justice Secretary, is expected to allow Sutherland’s release for him to spend his remaining time in a hospice.

Mr MacAskill faced an international storm last month when he made the decision to release Abdelbaset Ali Mohmed al Megrahi from the same prison on compassionate grounds because he is dying of prostate cancer.

Megrahi, who was serving a 27-year sentence for the bombing in December 1988 that killed 270 people, returned to Tripoli last month. Politicians from around the globe, including Barack Obama, criticised the decision to release him early.

The Justice Secretary is thought to have released approximately three prisoners on similar grounds in the past two years.

Glasgow MSP and Conservative Party justice spokesman Bill Aitken said last night: “When Alex Salmond’s government released Britain’s biggest mass murderer, the Lockerbie bomber, they made it nearly impossible to refuse any future release application. I only hope this time, they have impartial and independent medical advice to back up the decision.

“This is the sort of situation that we’d always warned him [Kenny MacAskill] about. He set a precedent with the decision to release Megrahi, and one wonders if it’s possible for him now not to release anybody in cases of this sort.”

A spokesman for the Scottish Government said, however: “The law allows prisoners with less than three months to live to apply for early release, and due process has been followed. The Cabinet Secretary approved the compassionate release following that process.

“If a prisoner makes an application, the Cabinet Secretary is duty bound to consider that application, and that’s what he did.”