Democratic Alliance (DA) leader Helen Zille said on Tuesday that the African National Congress (ANC) has left behind former President Nelson Mandela's vision of a country in which the Constitution gives everybody the right to dignity.

Instead, Zille said at a ceremony marking the twentieth anniversary of the day that then-President FW de Klerk announced Mandela's imminent release, the "constitutionalists" in the ruling party were losing the battle for its soul.

"The group in the ascendancy believes that liberation means unfettered power to impose its will."

She said that the past year in politics had proven that "a Constitution can be effectively nullified without changing a single word of it".

"This happens when the institutions that are supposed to limit the power of the ruling party, merely become an extension of the dominant clique in the ruling party.

"When this happens the entire purpose of constitutionalism is subverted, so that it protects the party and not the people."

Zille said constitutionalism was built around the notion that no ruler or ruling party, not matter how popular, can do as they please.

She said that this notion was not integral to liberation movements, but that there had been hope when Mandela took power that the ANC could defy African precedent and make a successful shift to being a political party.

"There was a general understanding and acceptance of the need to limit power to avoid the mistakes of the past."

She likened the supporters of President Jacob Zuma to France's 18th century Jacobins, who seized power after the revolution and defined themselves as constitutionalists but executed opponents in their bid for centralised control.

"They are guided not by the Constitution which guarantees each person indivisible rights but by the general will, which they define arbitrarily, as they please, to achieve their goal of absolute power."