MPs told Correctional Services Minister Sibusiso Ndebele that the release had not been transparent.

Selebi was released from Pretoria Central Prison on the recommendation of the 11-member Medical Parole Advisory Board so that he could receive treatment for kidney failure.

At the time of his release, Selebi had served only 229 days of the 15-year sentence handed down by the Johannesburg High Court for corruption.

Questions over his release persist, with critics suggesting he enjoyed preferential treatment because of his political credentials.

DA MP James Selfe said Selebi's release could not be divorced from that of fraudster Schabir Shaik, who was said to be "terminally ill".

"The real problem that we face in this system is around the credibility of the medical parole system as a whole . because what we have is a very clear situation of a particularly high-profile member of the ruling party who is as fit as a fiddle and swans around Durban playing golf and living the high life.

"So when another high-profile member of the ruling party is released on medical parole, you have a credibility problem. The person on the street does not believe that the system works properly," Selfe said.

Another MP, Bushy Mnguni of COPE, said the legitimacy of medical parole had become tainted.

"We must try to resuscitate [it] and to make it fair," said Mnguni.

But the national commissioner of Correctional Services, Tom Moyane, defended Selebi's parole, saying it had followed the law to the letter.

He said the parole board, a statutory body of the department led by Dr Victor Ramathesele, had overseen the entire process to release Selebi.

"In this particular instance, I believe we have done what is acceptable by law, and within the parameters of ethics within which we practise," said Moyane.

"I would like to believe that had it not been because of the profile of the individual, it could have been something different . but I say that the treatment of inmates is equal before all correctional officials in our department."

Moyane said that in the same month Selebi was released, the parole board had considered 12 requests for medical parole, including from three applicants who had died while their documentation was being processed.

No application had been received from Clive Derby-Lewis, who is serving life for the murder of SACP leader Chris Hani, Moyane said.

Derby-Lewis's wife, Gaye, has told The Times she would apply for her husband to be released on medical parole on the grounds that he has prostate cancer.