Johannesburg - Former judge Willem Heath says President Thabo Mbeki has been "misled" and that's why he decided not to include the special investigations unit in the government's controversial arms deal investigation.

Heath was at the head of the unit when parliament asked it to investigate alleged irregularities in the negotiations leading to the signing of the arms deal.

He didn't mince words on Sunday when he launched a scathing attack on government's handling of the investigation into the multi-million rand deal.

Speaking at the Gauteng launch of the Independent Democrats, the new party started by Patricia de Lille, Heath criticised the president's advisers who, he said, had "misled the president on purpose" about the unit's role in the investigation.

"The process was inherently at fault and justice and transparency were impeded because there was no judicial or factual reasons to exclude the unit."

Heath is a friend of De Lille's. She says both of them are "victims of the controversial arms deal".

At the time, Mbeki didn't give permission for the unit to be involved, although parliament's standing committee for public accounts requested its involvement. In the midst of allegations of executive interference at parliamentary level, the investigation was left in the hands of the auditor-general, the public defender and the national director of public prosecutions.

Evidence has in the meantime surfaced that the conclusions of the investigative team have been distorted through political intervention.

Heath described the action of the "relevant minister", Dr Penuell Maduna, minister of justice, as an "outrage of applying the law", because Maduna insisted that the unit "showed evidence that left no cause for doubt" why he had to investigate the arms deal.

With acknowledgements to Mandy Rossouw and Beeld.