The NNP won just 2% of the vote in last year's elections
The New National Party (NNP) suffered a big defeat in the general election last year, taking less than 2% of the vote.
Mr de Klerk said the party's demise would weaken opposition to the ruling African National Congress (ANC).
He told the BBC that a new party was needed, but without the National Party's historical baggage.
The National Party introduced apartheid in South Africa in 1948, and governed until democratic elections in 1994.
Its successor party's federal council agreed by 88 votes to two on Saturday to disband.
Vacuum
"I really believe that the dissolution of the national party creates a void in the party political scene in South Africa," Mr de Klerk said.
We need a fairly young person without any political baggage to stand up and be counted
FW de Klerk
"We need a fairly young person without any political baggage to stand up and be counted and say 'we are going to fill this void'."
"I think there is a need to establish something to take the place of the National Party, but hopefully without the historical baggage which the National Party carried and which also played a role in its demise," he added.
The party pulled out of the government in 1996 and was relaunched to try to make a break with the past.
But last year's election saw the NNP win just seven seats in parliament.
'Injustice'
This prompted the party to join forces with its former enemy, the ANC, which took over in the first multi-racial elections.
However, it failed to carve out a new identity for itself.
The party will formally cease to exist after the forthcoming local government elections, which it will not contest.
Party leader Marthinus van Schalkwyk apologised for the apartheid years under the National Party, which he said was "a system grounded in injustice".
Mr van Schalkwyk is currently minister for environment and tourism.
He said the dissolution of the party was throwing off the yoke of history and was their contribution to finally ending the "division of the South African soul".
O ex-partido de apartheid na África do Sul, o Novo Partido Nacional (NNP), foi finalmente dissolvido por um voto do conselho federal do partido no dia 9 de abril de 2005. A votação foi de 88 votos a favor, 2 contra, e 3 abstenções.

A decisão segue uma orientação do ano passado  do líder de partido Marthinus van Schalkwyk   para juntar forças com o partido do governo, o Partido do Congresso Nacional africano  (ANC). "O precursor do NNP, o Partido Nacional, trouxe o desenvolvimento para uma região  da África do Sul,  mas também trouxe o sofrimento através de um sistema construído sobre a injustiça," disse  van Schalkwyk.

O NNP foi o sucessor do Partido Nacional, e recebeu o novo nome em 1997 para distanciar-se do antigo  apartheid. O Partido Nacional foi o partido do  governo da África do Sul de 1948 a 1994, e promoveu políticas de apartheid e a promoção da cultura  africânder.