This comes after the bank served Fraser with a notice last week that it intended to close his accounts on May 22 for alleged reputational risk.
In a statement on Monday, Fraser implied that the bank was part of a plot to discredit him and eventually force him out of the public sector.
Independent Media reported over the weekend that Fraser was among 15 people under investigation for various alleged crimes, including murder, corruption and money laundering.
It is understood that Fraser, who was redeployed as the country’s prisons boss by President Cyril Ramaphosa last year, is facing accusations of corruption related to the alleged looting of the SSA slush fund when he was the country’s spy boss.
Fraser said: “Nedbank has inexplicably targeted my family, that is, my son Lyall Fraser and my brother Barry Fraser.
"I remain in the dark about the nature and details of the alleged reputational risk, if any, that may have led to Nedbank making what I view as an unjustified decision.
"This comes after my lawyers have just given notice to Jacques Pauw’s attorneys, advising that I would be filing a defamation (suit) against him for the false and defamatory statements contained in his recent book, The President's Keepers, about me and my family.”
Citing media reports about the possibility of his being arrested, Fraser said there was a campaign by certain individuals within and outside the state "not only to destabilise the country but also to target independent and professional senior government officials who refuse to be drawn into their political machinations”.
He added that this followed his decision to implement the old Special Investigating Unit recommendations regarding the allegations of corruption against Bosasa.
Fraser said: "I am fully aware of unlawful and unethical parallel clandestine operations to discredit and remove me from the public sector. I hope Nedbank will not allow itself to be part of such illegality.”
Fraser maintained that even Ramaphosa’s affidavit indicated, in a matter between the president and the DA, that he couldn’t be dismissed from his new job based on “hearsay allegations”.
Fraser’s lawyer, Rapulane Kgoroeadira, said on Monday he found it odd that the bank intended to close his client’s accounts.
“Yet no law enforcement agency has ever contacted us to indicate that my client is under any investigation.
"It is very odd and we really don’t know what is the issue here,” Kgoroeadira added.
Nedbank spokesperson Kedibone Molopyane said on Monday night: “As per Mr Arthur Fraser’s statement released today, Nedbank can confirm that it did issue him with a client termination notice.
"However, we cannot disclose details of the reasons or further client information.”