President Thabo Mbeki, the leader of the ANC, on Sunday described the New National Party's decision to join the ANC as an historical development, SABC news reported.
Mbeki was speaking at a Women's Day event organised by the ANC Women's League at the Sandton Convention centre.
Mbeki could not recall any other party of oppression saying, "we are defeated, we cease to exist, we join those that we had oppressed."
The ANC said in a brief statement on Sunday: "The ANC views this move as a positive step in South Africa's political development and believes it will contribute to building an inclusive and nonracial society."
Meanwhile, Pieter Mulder, leader of minority party the Freedom Front Plus, said the NNP's decision was an embarrassment for everyone who had ever been associated with the party.
"Not one of the founding members of the National Party in 1914 or any of the party's previous leaders could have predicted that the party would be destroyed in such a tragic and dishonourable way by being swallowed up by the ANC."
He suggested that NNP members of parliament cross over to his party, rather than the African National Congress when floor crossing opens in September.
"The FF+ invites them (the NNP councillors) to retain some of their political integrity and cross over to the Freedom Front instead of the ANC," Mulder said.
Following the announcement on Saturday that the NNP would fight all future elections under the banner of the ANC, NNP leader and Environmental Affairs and Tourism Minister Marthinus van Schalkwyk had encouraged NNP members of Parliament to cross over to the ANC, saying they would retain the positions they hold if they did so.
He himself would join the ANC "within a few weeks," he said.
The ruling party's seats in the National Assembly will rise to 286 if all seven of the NNP's MP's join the ANC.
Mulder further said no one who believed in democracy would be able to understand how it could be in South Africa's interest to make the ANC even stronger than its 70 percent election victory.
He reiterated the FF+'s standpoint that "the answer lies in constructive opposition".
He said the NP after 90 years had finally reached the end of the road, and that soon all signs of the NNP would be wiped out.
Democratic Alliance MP Helen Zille also said the latest NNP/ANC agreement was the final nail in the NNP's coffin. She said van Schalkwyk had destroyed his party and abandoned his voters in return for a cabinet position.
"This agreement is the price he has to pay and has got nothing to do with political principle."
"The excuse the NNP has given to justify this merger - that the debate about the future of South Africa can only take place inside the ANC - is absolutely misplaced," said Independent Democrats leader said Patricia de Lille.
"Parties do not need to be swallowed by the ANC in order to debate the future of our country. The debate about the future of South Africa must take place amongst all South Africans including many who are outside the ANC. The name of the ANC is becoming longer and longer it's now the ANC-NNP-COSATU-SACP alliance - without adding any substance to the deepening and strengthening of our democracy."
The Christian Democratic Party's (CDP) Federal Leader Rudi du Plooy said he was not surprised at the NNP's declaration that it would cross the floor to the ANC.
"The NNP has failed dismally in its attempts to regain its former glory days when it was still the NP. The uncertainty that surrounded the NNP was stretched to the limit and voters turned out in vain to try and resuscitate this dying party." - Sapa