Young Communist League leader Buti Manamela says Archbishop Desmond Tutu is "vomiting" on the graves of liberation heroes.
He also accused Tutu of encouraging people to follow his example.
"We respect his democratic right not to vote but we don't believe he should be mobilising people not to vote," Manamela said.
He said by doing this Tutu was vomiting on the graves of the dead liberators of the country.
He said God should not listen to Tutu's prayers for people not to vote.
"I am calling on the youth of this country to defy Tutu and vote in their numbers," he said.
Manamela, who was at a rally in Atteridgeville, Pretoria, at the weekend also lashed out at ANC dissidents.
He called them "mercenaries and Okapi-wielding thugs who accidentally found themselves in the ranks of the ANC during the apartheid era.