Basson, who practises as a cardiologist in Cape Town, is fighting charges of unethical and unprofessional conduct before a professional conduct committee of the Health Professions Council.

It is alleged that he had acted unethically while he was the project leader of the Defence Force's chemical and biological warfare programme in the 1980s and early 1990s.

American medical ethics expert Prof Steven Miles earlier testified that Basson's involvement in the large scale manufacture of drugs and teargasses, putting teargas in mortars, providing substances for across-the-border kidnappings and providing operatives with cyanide for suicide purposes, was unethical.

Salie Joubert, acting as pro forma complainant, on Tuesday hammered Basson with questions about his involvement in the project as a medical doctor.

Basson accepted that he had been registered as a medical doctor while he headed the project, but maintained he had acted as a soldier and not a doctor and that he had used his chemical and military knowledge rather than his knowledge as a medical doctor.

"It does not mean I practised as physician. I spent two and a half years of my life being trained as a soldier. I even acted as a bomb disposal expert," he said.

He denied trying to play on the tribunal's emotions by showing a video clip of a civilian being murdered when referring to his co-operation with the police by supplying them with teargas for crowd control.

He admitted that an attack on a civilian was not a chemical attack, but denied approving as a doctor the use of "chemical weapons" (in the form of teargas) on the civilian population.

"The police have been bombarding the population with teargas over the past three days even though there was not any chemical attack," he said.

Basson earlier testified that he had co-operated with the police by supplying them with tons of teargas manufactured by the project for crowd control, but said that decision should be seen in the context of the "mad times" of the 1980s.

He also admitted that Angolan rebel movement leader Jonas Savimbi had been supplied with mortars armed with teargas manufactured by the project, but insisted the aim was to protect the South African soldiers who were always with Savimbi and allow Savimbi to escape in an attack situation.

He denied trying to create the impression during his criminal trial (he was acquitted ten years ago) that the teargasses manufactured by the project were poisonous.

"We had no lethal weapons. We had a lot of deadly chemicals, but it was used for testing," he said.

Basson testified that he had been under the command of the Surgeon General and a co-ordinating committee at all times, but admitted that some of his orders came directly from the head of the Defence Force and other top officers.

He said General Neil Knobel, who was the surgeon general in the mid 1980s was sometimes sent out during top secret meetings with the Defence Force top brass and he remembered Knobel had problems with the command structures and selective orders that were given.

"I remember telling him I'm tired of having 120 bosses," he said.

Asked if he appreciated that Knobel was concerned that he was being given orders that did not fit in with his ethics as a medical doctor, Basson answered that he had never violated his feelings about ethics in his actions both as a doctor and soldier.

"What I did was not unethical. Those substances (such as mandrax, cocaine and teargas) did not have the potential to kill. "The intention has to be kept in mind.. Those substances were less toxic than paracetamol. I had no moral or ethical objections against it... The purpose was to save lives and minimise loss of life," he said.

Joubert accused Basson of lying to the commission in his plea explanation, in which he said all drugs manufactured by the project were for research purposes and were never used in combat situations, but Basson denied lying and said his plea only contained what he thought was necessary.

Joubert put it to Basson that the mortars supplied to Savimbi had been imported from Israel, that the teargas canisters were manufactured with Brazilian steel and the fuses came from China so that it could not be traced back to South Africa.

"The only conclusion is that those untraceable mortars were also used to break up crowds somewhere in South Africa.. They were waging chemical war against the population which they now want to justify.

"This is the type of chemical war on the population of this country you supported as a medical doctor," Joubert said.

Basson replied that the mortars used in Angola had absolutely nothing to do with crowd control in South Africa and that he had no say in the Head of the Defence Force's decision to supply the mortars and teargas to Savimbi.

Joubert earlier also put it to Basson that he was telling half truths about the reasons why former president Nelson Mandela had decided to re-employ him as a civilian in the Defence Force in 1995.

Basson said the reason was because the Americans and British governments had regarded him as a threat and wanted to employ him as a chemical and biological warfare consultant to contain him.

Joubert put it to him that the Americans and British feared that Basson would supply information to the Libyans and had asked former president Mandela to restrict Basson's movements, but that Mandela had refused because he had fought restrictions his whole life.

Joubert said the surgeon-general had then suggested to Mandela that Basson should be re-employed in the military to contain him.

The hearing will continue on Wednesday.