The graft case against President Jacob Zuma carried "utmost gravity" and he was part of a broad corruption scheme intended to benefit the ANC in perpetuity, Beeld newspaper reported on Friday.
The case against Zuma was strong and would also show that the ruling party was meant to be an "eternal beneficiary" in an "extended scheme of corruption", senior National Prosecuting Authority prosecutor Billy Downer, who wanted to prosecute Zuma, wrote in a memorandum in 2009.
The memo was addressed to then acting national director of public prosecutions Mokotedi Mpshe, Beeld reported.
A month later, Mpshe dropped the corruption charges against Zuma.
In the memorandum, obtained by Beeld, Downer wrote that the case against Zuma carried "utmost gravity".
He said the Scorpions investigation originated in the arms deal probe, but the ultimate investigation and the basis of the indictment was only fractionally related to the deal.
Downer wrote that in reality it was an "overriding and pervasive scheme of corruption", designed to be of extraordinary duration and ultimately to keep Zuma indefinitely on the payroll of the company of his former financial adviser Schabir Shaik.
Both the Zuma and the ANC would benefit from this scheme.
"The mode of conferring benefits on Zuma extended to the ANC and Zuma in his capacity as the highest office-bearer of the ANC which was also to be an eternal beneficiary in the extended scheme of corruption," Downer reportedly wrote.
"To accede to the representations in a summary manner would abandon all the ground won by the expense of extraordinary effort and resources and with the approval of the highest courts in our country.
"A retreat for no good reason at this stage would not be explicable, understandable or defensible."
Mpshe announced on April 6, 2009, that the charges against Zuma would be dropped because there was a political conspiracy against him.
Shaik was found guilty of corruption and fraud in 2005. He was sentenced to 15 years in jail, but served only two years before being released on medical parole.