The publisher billed the book as the result "of five years of travelling and interviewing eyewitnesses and piecing together a mountain of evidence".
Basti alleges that Williams and Dunstan used evidence he had spent years putting together. Williams, a British TV journalist, and his co-author firmly deny the claim.
"Basti did in no way invent the idea of Hitler being alive in Argentina," Williams said. "Books on the subject existed as far back as 1953."
Williams travelled in 2007 to Argentina where, he acknowledges, he received help from Basti, along with other researchers and translators. Basti claims that on seeing the book and hearing of the new film he realised that work he had handed over to Williams for use on an earlier documentary had been plagiarised.
Basti says he signed a contract conferring all rights to his work to Williams' company in return for substantial payments to come.
Filming began in September 2008, but was cut short when financiers pulled out due to the worldwide financial crisis. Basti claims his contract was terminated and so asked for his research to be returned but says nothing was sent back.
The claims about Hitler's life in Argentina have been ridiculed by historian Guy Walters, who pronounced them "2000% rubbish" when the book came out.
"There's no substance to it at all. It appeals to the deluded fantasies of conspiracy theorists and has no place whatsoever in historical research."
- Observer