His scandalous comments given in a newspaper interview, in which he accused former president Thabo Mbeki of masterminding the laying of criminal charges against Jacob Zuma before he assumed leadership of the ANC - proved beyond doubt that Heath cannot carry on the duties at the SIU with the kind of dignity and independence demanded of anyone holding such office.
There were already too many questions about the wisdom of appointing Heath to such an important post, given his recent associations with President Zuma.
The former judge had acted as one of Zuma's legal advisers when the ANC leader was charged with - and later acquitted of - rape. Heath was also part of the legal team that devised a strategy to rescue Zuma from a corruption trial that threatened to block his rise to the presidency of South Africa.
But Heath's latest utterances, in which he also cast aspersions on the fraud and corruption conviction of Zuma's friend Schabir Shaik, have irrefutably demonstrated that his remaining at the SIU can only harm the anti-corruption unit.
Zuma has promised an investigation into whether Heath held grudges against certain individuals and whether this has made him unsuitable for office. The president has refused to set deadlines for the probe.
While an investigation should be welcomed, Zuma should either suspend Heath or encourage him to go on leave while the matter is being considered.
Better yet, if he had any sense of dignity left, Heath should tender his resignation - saving the SIU and the office he holds from the irreparable damage that would certainly be caused by his remaining in the post.
The fight against corruption is a do-or-die affair for the country, one that cannot be won if institutions created to lead the battle end up in the hands of people who are more concerned with settling old personal scores.
Zuma and Justice Minister Jeff Radebe owe it to South Africa to ensure that Heath's successor is a truly fit and proper person for the job.
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