This would include such areas as evidence and intervention by the old Progressive Party and Progressive Federal Party at the time of the 1960 Sharpville shootings and the death of black consciousness leader Steve Biko in 1977, and the PFP's role in monitoring unrest, he told Sapa in an interview.
Leon said he hoped to share the making of the DP's submission to the TRC - possibly on Tuesday - with Progressive veterans like long-standing human rights campaigner Helen Suzman and former PFP leader Colin Eglin who had been "around at the time" (when gross human rights abuses were committed during the apartheid era).
He was in the process of contacting Suzman on her availability.
Leon said the DP had initially decided not to make a submission to the TRC as it had viewed the body more in the light of a "confessional".
The DP and its predecessors had not been involved in any human rights abuses or atrocities.
A strong body of opinion within the party had argued, however, that the party should put on record the anti-apartheid and human rights-abuse monitoring role which it and its predecessors had played.
The DP Parliamentary caucus had on Thursday accordingly decided to reverse the previous stance.
The party was now working "flat-out" to prepare the submission.
Other areas it would cover would include why the DP and PFP had participated in the Tricameral Parliament - and what they had achieved by doing so - and to "put at rest" a perception, especially the townships, that the DP or its predecesors had been party to decisions to conduct cross-border raids.
- With the DP's decision to give evidence to the TRC, the only Parliamentary party which is now not scheduled to do so is the IFP.
All the hearings are to be conducted in Cape Town next week, with Deputy President Thabo Mbeki to lead the ANC's case and NP leader F W de Klerk his party's.
General Constand Viljoen will make a submission on behalf of the Freedom Front and Clarence Makwetu on behalf of the PAC. MP Louis Green will put the ACDP's case.