Penguin Books has defended one of its authors, a Spanish military colonel, against accusations of antisemitism, insisting that his views are instead merely “robust”.

Pedro Baños’s book, How They Rule the World, was published by Ebury Press, a division of Penguin Random House, in April.

But British spy fiction author Jeremy Duns highlighted issues with the text, noting its front cover features octopus tentacles, which have long been associated with antisemitic propaganda.

Mr Duns found that, unlike the English translation, the Spanish version made several references to the Rothschild family, including a passage accusing the banking family of holding “gigantic” economic power and influence which has “led to multiple speculations about their capacity to intervene in key global decisions”.

Mr Duns argued the omission of these passages was proof that Penguin knowingly published a book by a “Spanish antisemitic conspiracy theorist”.

A colonel in the Spanish army, Baños was previously the chief of counter-intelligence and security for the European Army Corps.

In interviews with Spanish media, he has called the Rothschilds dominant and likened them to the Illuminati. On Spanish TV, he also once accused Israel of being behind the assassination of John F Kennedy.

Penguin told the Guardian that Mr Duns’s critique had prompted a review of Col Baños’s work, saying it was aware of “serious concerns”.

It concluded that, while the author expressed “robust opinions about geo-strategies and geopolitics… he does not in our opinion express views in this publication, including in the parts omitted, that are antisemitic”.

It said: “As a publisher who takes our responsibilities to our readers and our authors extremely seriously, we always undertake careful due diligence before committing any book to publication, and this book was no exception.”

The publisher also defended using an image of octopus tentacles on the front cover, saying it reflected “domination by an imperialist power”.

The Campaign Against Antisemitism urged Penguin to withdraw the title and "investigate who is responsible for the decision to publish and translate it".

"Conspiracy theories are often the vector for antisemitism and should not be perpetuated by reputable publishers," it added.

Last week, Col Baños tweeted: “Classic disqualifications to discredit the work of a critical author with power: 1. Non-academic 2. Anti-system 3. Communist 4. Populist 5. Pro-Russian 6. Antisemite. Please spies and cronies: Have a little more imagination!”