"Often this method only succeeds in accommodating the leaders without the supporters of these parties overwhelmingly supporting the merger."

The Democratic Alliance's "swallowing" of other parties results in many anti-ANC votes which would go to the Independent Democrats and Agang SA being lost, the FF Plus said on Monday.

"The DA's way is to merge with other parties while the DA still retains its identity," Freedom Front Plus leader Pieter Mulder said in a statement.

"Often this method only succeeds in accommodating the leaders without the supporters of these parties overwhelmingly supporting the merger."

The failure of the DA-Agang SA merger proved this.

Mulder said co-operation between opposition parties was essential to end the African National Congress's dominant position in the country, but the question was what type of co-operation was best.

On Sunday, the DA announced that Agang SA leader Mamphela Ramphele had gone back on an agreement to stand as the DA's presidential candidate.

Both Zille and Ramphele held separate press briefings on Monday to explain what happened.

Ramphele said the decision was rushed into and the technical issues of a partnership were never ironed out.

Zille, on the other hand, disagreed.

On Sunday, Zille lashed out at Ramphele, accusing her of playing cat and mouse games.

The African People's Convention on Monday said the deal between the DA and Agang SA had nothing to do with a desire to change the political landscape for the good of the country.

"It was an elitist agreement of personal friendship which failed at that level," APC president Themba Godi said in a statement.

"APC condemns DA for using black people to protect white interest. What Ramphele has done was political fronting of note."

Godi called on those who believed they had been misled into joining Agang SA to vote for the APC.