Opposition parties are calling for an investigation into the release of convicted fraudster Schabir Shaik on medical parole.

The Democratic Alliance said it would write to the Health Professions Council, asking it to probe the "serious anomalies" it saw in the decision.

The United Democratic Movement, in an open letter to President Kgalema Motlanthe, asked him to launch an investigation, saying Correctional Services Minister Ngconde Balfour's "bellicose attitude" had done nothing to inspire confidence.

The Congress of the People would write to the National Director of Public Prosecutions (NDPP) asking it to probe Shaik's "sudden release".

They were responding to a report in the Sunday Times that head of cardiology at Albert Luthuli hospital, Professor DP Naidoo, personally discharged Shaik in November as he was considered well enough to leave.

However, the correctional services department never sent him back to prison. He instead remained there until his parole this week.

Naidoo was quoted as saying that he had been told by hospital management that Shaik's discharge from the hospital was "in the hands of hospital management and correctional services".

According to the DA's spokesman on correctional services James Selfe all evidence available to the public indicated Shaik was not in the final phase of a terminal disease.

Final phase of terminal illness?

"The onus is on the medical practitioner to judge whether an offender can be classified as being in the final phase of a terminal condition... At present, the evidence available to the public suggests that Mr Shaik is suffering from an illness, but is not in the final phase of a terminal illness," he said in a statement.

Selfe said Parliament's portfolio committee on correctional services was informed on 12 August last year that Shaik was ill, but was not terminally ill.

"We believe that the HPCSA can and must conduct an inquiry that will ensure that professional medical standards are being upheld. Notably, this inquiry will be able to determine whether any irregularities occurred, without necessarily publishing confidential information pertaining to Shaik's medical condition."

UDM leader Bantu Holomisa, in his open letter, wrote of Balfour: "With every new revelation his behaviour seems part of a broader conspiracy to undermine the rule of law in order to grant Mr Shaik freedom when he should be serving time in prison.

He said Balfour was doing everything in his power to ingratiate himself with the incoming administration to ensure his re-appointment.

Holomisa proposed a three-person commission probe the matter. It should consist of a judge and two respected medical practitioners who specialised in Shaik's "alleged condition" to interview everyone who had been involved in his treatment.

Cope spokesman Sipho Ngwema said in a statement the NDPP should demand a "full explanation" from correctional services, the national council for correctional services and the parole review board, headed by Judge Seraj Desai, on why Shaik was released.

Shaik was sentenced to 15 years in jail in 2005 on two counts of corruption and one of fraud, which, among other things, related to an alleged bribe he negotiated between ANC president Jacob Zuma and a French arms company.

He has been in and out of hospital at least four times since his imprisonment.