Jean Prieur du Plessis told the commission's amnesty committee in Pretoria he had also envisaged military bases in Namibia, Mozambique, Angola and Zimbabwe. The operation was to have been funded by a diamond smuggling syndicate and armed robberies.
"We would have robbed armoured cars and banks to buy land and to get the syndicate going," he said.
Du Plessis is serving a 12-year jail sentence for several crimes, and has applied for amnesty. He was in September 1993 convicted on counts of robbery, theft of weapons from the SA National Defence Force, and the illegal possession of firearms.
He testified that he had been the leader of an ultra-rightwing organisation, the Nationalist Socialist Partisans (NSP). The movement had only four members and was set up in July 1991. Two members had died after clashing with the police and the third is serving a life sentence for murder.
The NSP subscribed to Nazism, adopted the Swastika as its emblem, and regarded Jews as being part of a sinister force controlling the world through their wealth.
"We believed the white man was the highest from of life. In our minds, whites were the only people entitled to exist," he said.
The underground body was supposed to have prevented blacks from taking over the governments of South Africa and Namibia.
To this end, du Plessis, a first-year BA student at Pretoria University at the time, had mapped out a grandiose strategy, which included making contact with rightwingers overseas.
The first step was to acquire weapons. In their first attempt to steal firearms, from a private Louis Trichardt home in Northern Province, two members of the group murdered three people. Du Plessis did not take part in the murders in October 1991.
"The deaths upset and flustered me," he said.
The group, however, felt they were beyond the point of return and decided to go ahead with their plans. They succeeded in stealing ammunition from an SANDF base at Potchefstroom and a few R3 rifles from Wallmahnstall military base north of Pretoria.
"I then decided it was time to rob between R3 and R5 million to buy a farm in Namibia for our first military base," du Plessis said.
Similar bases would eventually be set up in neighbouring countries, Europe, Britain and the United States.
During this time du Plessis had made contact with French rightwinger Olivier Matthieu, who later informed the group that he had recruited five Italians, who had already started training.
Du Plessis said the overseas cells would have countered negative international reaction once the NSP and its allies had succeeded in declaring an Afrikaner state in South Africa.
He said he had discussed the outline of his plans with other leading rightwingers, such as former senior Afrikaner Weerstandsbeweging member Dries Alberts and Anton Terblanche of the Boerestaat Party.
Alberts had donated R2000 to the NSP.
Asked how somebody at his youthful age could influence senior figures, du Plessis said he had been very inspired and had a clear vision of the future.
"I believe I am a good orator, able to persuade people," he added. "I believe I am a strong leader."
Du Plessis said he had since renounced violence as a means to achieve political change.
"The peaceful transformation in South Africa in 1994 was incredible. I was very surprised as I had been convinced there would be violence and murder."
He was converted to the Christian faith in December 1994, and earlier this year he started a church, the United Christian Mission, in prison.
"I deliver a sermon once a week," du Plessis said. "Christ is our only hope in this country."
He added that he had resumed his BA studies, and was thinking of becoming a missionary upon his release from prison.