[citation needed] It became the official opposition in the whites-only House of Assembly of South Africa in the elections of 6 May 1987, when it surpassed the liberal Progressive Federal Party, winning 550,000 votes.

The Conservative Party led the "no" campaign during the 1992 referendum, when white South Africans were asked to determine whether or not they supported the negotiated reforms started by the government.

Apart from Treurnicht, the official Leader of the Opposition, and Clive Derby-Lewis, the Shadow Finance Minister, the no side was supported by former President P W Botha, who denounced de Klerk's reforms as irresponsible and perilous to the stability of the country.

Clive Derby-Lewis was found guilty in 1993 (under the emergency legislation enacted by the House of Assembly) of involvement in the assassination of South African Communist Party leader Chris Hani.

The decision not to participate in the first non-racial parliamentary elections in 1994 resulted in much of its support base defecting to the newly formed Freedom Front, another party of similar views which had been joined by one of its MPs Pieter Mulder.

The merger was consolidated when its remaining two municipal councillors joined the FF+ during the September 2004 floor crossing period, thus bringing a formal end to the Conservative Party.