A call by former intelligence minister Ronnie Kasrils for voters to either not vote for the African National Congress (ANC) or spoil their ballots is "reactionary", the ruling party said on Tuesday.

"The ANC regards this call espoused by the Vote No Campaign as disruptive, reckless and counter-revolutionary," spokesperson Jackson Mthembu said in a statement.

"Reactionary statements therefore that call for such careless behaviour as spoiling ballot papers is tantamount to undermining the long struggles and the sacrifices of our people."

Kasrils and other African National Congress stalwarts have been criticised by the party for their "Sidikiwe! Vukani! Vote Campaign".

Earlier on Tuesday, the group said it was not a "no vote" campaign – they were calling on people to go to the polls on May 7 and not vote for the ANC.

Former deputy health minister Nozizwe Madlala-Routledge, who was part of the campaign, said citizens could send a strong message by either voting for a minority party, which would take away from the dominant political parties, or people could spoil their ballots.

Mthembu said the ANC was confident Kasrils's call would have no impact on the party or the elections.

"On the contrary, we believe that it will galvanise more of our people to go out on the 7th May to show Kasrils and ilk that the right to vote is sacrosanct."

The Workers and Socialist Party (Wasp) said the campaign was not a solution to anger with the ANC.

"We... appreciate their desire to do something about it," Wasp said in a statement.

"But we disagree with the campaign's founding statement because it does not offer a clear alternative to the ANC or the other capitalist parties."

With three weeks to go until the election, it seemed unlikely that the campaign would build momentum.