Ramaphosa's letter has been seen as a preemptive strike ahead of a crucial special sitting of the ANC's national executive committee this weekend.
The president bemoaned the scale of corruption tainting the party, saying the ANC stands in the dock as accused number one.
Hitting back at Ramaphosa, the former president said it is “unforgiveable” that he label the organisation as accused number one when it is individuals in the party who stand accused of wrongdoing. He then turns the tables on Ramaphosa, saying he needed to come clean on his business interests and rise to power.
“To point at the entire ANC and its ordinary working class members is rather low and disappointing, to say the least. Presently formulated, your letter lends credence to the suspicion that you seek to assist those, in our ranks, involved in attempts to destroy the ANC in order to hand it over to be a tool of white monopoly capital interests.
“Maybe, Mr President, this is the opportune time to tell our members whether, during the so-called 'nine wasted years', any of your companies did business with government (national or provincial) while you were deputy president of our movement and the country.
"This would help you, Mr President, to dispel this unfortunate allegation, sometimes directed at you. It is individuals from the ANC who must bury their heads in shame, not the ANC, our glorious movement," wrote Zuma.