HPCSA spokesperson Bertha Peters-Scheepers said they had received a complaint from the Democratic Alliance and would immediately start the investigation.

James Selfe, DA spokesperson on correctional services, said the decision to release Shaik was made on the advice of the three doctors.

He said the HPCSA should determine whether the doctors acted in compliance with the rules.

"In terms of the procedure followed by parole boards, the medical practitioner(s) must state both that the illness is terminal, and that the offender is in the final phase of that terminal disease or condition... in other words an assessment has to be made of life expectancy of the offender," Selfe said in a statement.

Shaik was granted medical parole after serving two years and four months of a 15 year sentence.

He had been found guilty on two counts of corruption and one of fraud, which, among other things, related to an alleged bribe he negotiated between African National Congress president Jacob Zuma and a French arms company.

Controversy exacerbated by ties with Zuma

Selfe said the controversy around Shaik's release on medical parole had been exacerbated by Shaik's close ties with Zuma as well as the statement by Zuma that he would consider pardoning Shaik if it was legally possible [only days before Shaik's release on medical parole].

Another controversy, he said, was a statement by Professor DP Naidoo, the head of cardiology at Inkosi Albert Luthuli hospital, that he had "personally" discharged Shaik from hospital in November last year because he considered him well enough to return to prison.

Selfe said the ethical and professional rules of the HPCSA stipulated that "a practitioner shall not permit himself or herself to be exploited in any manner".

He said should it emerge that the three doctors involved in approving Shaik's release had been influenced by any individuals to reach a decision based on non-medical criteria, this might constitute exploitation in terms of the rules.