Kunene's outburst was triggered by Vavi's statement about political high-flyers who he says make him sick by spending their time eating sushi from the bodies of half-naked women.
Kunene, who co-owns ZAR Bar Lounge, an expensive nightspot in Sandton with business partner Gayton McKenzie, celebrated 40 years on October 21 at a party that was reported to have cost R700,000.
He also describes himself as an executive shareholder of mining company Rand Gold.
He said in his letter he spent more than R700,000 and he would have a follow-up party in Welkom this weekend to which "Vavi is not invited".
Kunene describes himself as self-made and does "not hide behind his wife's businesses like Vavi. Unlike you, who did not address me directly in your comments to the media".
In his letter, Kunene agrees with Vavi that there is corruption in the country. "There is cronyism, nepotism, bribery and everything else that rolls off your tongue like a rap sheet from a police printer."
But he distances himself from these social ills. "I'm grateful that my businesses are successful and they allow me to buy the same things that others may have had to be corrupt to buy. But just because a corrupt official bought a sports car, and I also bought a sports car doesn't imply I'm also corrupt."
Vavi responded: "I won't be dragged down the mud with Kunene. "People won't be able to tell the difference between me and him, so I won't stoop that low."
Free State-born Kunene says he has never benefitted from any BEE deal. His party was attended by the who's who of business, celebs, soccer players, Julius Malema and President Jacob Zuma's spokesperson Zizi Kodwa.
Kunene writes: "You say that my so-called R700,000 party is a 'corruption of morality' and that I'm spitting in the face of the poor. I should not have to defend what I spend on a huge milestone in my life, when it's honest money and we were having honest fun."