The South African author of an explosive book that promises to expose “the darkest secret at the heart of Jacob Zuma’s compromised government” has vowed that he is not intimidated by efforts from the country’s state security agency to have the book banned from sale.

Investigative journalist Jacques Pauw’s The President’s Keepers is an study of what he calls “the people who have brought our country to the brink of a mafia state”. Moving from the Western Cape to Pretoria, Johannesburg and Russia, The President’s Keepers follows “a trail of lies and spies, cronies, cash and kingmakers as Pauw prises open the web of deceit that surrounds the fourth president of the democratic era”, says the publisher, NB.

Following publication on 29 October, the SSA served NB and Pauw with a cease and desist letter on 1 November, over what it called “unlawful publication of classified information”. The letter said the book was “replete with inaccuracies” and that it “compromise[s] the security of the state”, calling on Pauw and NB to withdraw the book and retract “all those parts which are inaccurate”.

Should they “fail to adhere to the above demands”, says the letter, the SSA will take the issue to the high court, and institute criminal charges. The South African Revenue Service (SARS) has also threatened legal action over Pauw’s investigation into Zuma’s tax affairs, according to South Africa’s Sunday Times.

But NB said that it stands by Pauw, with lawyers acting for the publisher and for Pauw telling the SSA’s lawyers that they will “not desist from making the book available to the public, will not withdraw the book from the market, and will not retract anything therein contained”.

Willem De Klerk Attorneys’ letter adds: “Your generalised statement that the book is ‘replete with inaccuracies’ is not backed up by a single reference to any specific statement in the book that is alleged to be inaccurate. Your demand for a retraction ‘of all those parts which are inaccurate’ is therefore incongruous. It is furthermore unclear how you reconcile an allegation of falsity, on the one hand, with an alleged violation of statutory provisions on the other.”

Pointing out that the book has been publicly available for more than a week, with thousands of copies already sold, the letter says that there is “no basis for an urgent court application to prevent the further distribution of the book”.

A pirated copy of the book has been shared widely on social media, prompting NB to ask readers to buy legal copies of the title. “We understand that many South Africans are doing this innocently, believing it to be a protest against the SSA’s attempt to have the book withdrawn,” said the publisher. “We assure the public the book is not banned and we are printing more to meet the overwhelming demand and working to get them to the shops as soon as possible.”

Pauw wrote on Facebook that he had been “inundated with requests from people who want to pay me for the free pdf copies of The President’s Keepers that they downloaded from the internet”, but that he was not going to take their money.

“This is not about money. It is about your support that is going to enable us to legally lock horns with SARS … and whoever else drags us to court. We face the potential of a multitude of legal challenges, both criminal and civil. If you read the book, you will realise that it is a tried and tested strategy of the state to legally wear out their enemies. This might well be another of those cases,” he wrote.

Pauw added that he expected the SSA to approach the high court on Tuesday.

“There is no way they are going to be successful. No court is now going to ban this book. If they charge me criminally, we will fight the charges tooth and nail,” he said.

He and NB were supported by the International Publishers Association, which called on the SSA and SARS to stop their attempts to have the book withdrawn, describing their efforts “to harass and intimidate Mr Pauw and his publisher [as] reminiscent of the old apartheid regime in South Africa”.

“The cruel irony cannot be lost on anyone observing these shameful actions,” said Kristenn Einarsson, chair of the IPA’s Freedom to Publish Committee, calling the threatened legal action “crude and ham-fisted attempts at censorship”.

Mpuka Radinku, executive director of the Publishers Association of South Africa, said that the moves “could be seen as a betrayal of the vision of a post-apartheid South Africa that the international community had welcomed. We are appalled that the SSA is trying to suppress freedom of expression through intimidation and threats of a cease-and-desist letter as a means to shield the government from embarrassing revelations.”