The king of Nelson Mandela's Thembu tribe defected from the ruling ANC to join the Democratic Alliance (DA) Monday, days after launching a fierce attack on President Jacob Zuma.

King Buyelekhaya Dalindyebo, who rules over Mandela's tribe in the Eastern Cape province, the ANC heartland, was photographed holding a DA membership card in a very public snub to the ruling party.

Last week Dalindyebo -- no stranger to controversy -- called Zuma a parasite, accusing him of being in the pocket of corrupt individuals.

Democratic Alliance (DA) spokesman Mmusi Maimane said although they do not agree with some of the king's statements "anyone is free to join the DA."

The king has spoken about his regular use of cannabis and has been charged with manslaughter, arson, assault and kidnapping.

"We believe that he represents an important component of society in the Eastern Cape," said Maimane.

The predominantly white party which runs the Western Cape province is trying to boost its profile in black areas ahead of the 2014 elections.

Dalindyebo was visited at his palace by DA regional leader Athol Trollip, after he expressed a desire to join the party.

Tribal chiefs in South Africa are seen as crucial for tapping the rural electorate, which bears the brunt of poverty and lack of services.

The controversial king claimed joining the party would be a gift to the ailing Mandela, whom he has visited in hospital.