Nazi leader Adolf Hitler did not die of suicide by cyanide in Berlin in 1945, but he killed himself and died an old man in Argentina, a new book by British authors had claimed.

British journalist Gerrard Williams told Sky News he and co-author Simon Dunstan found an "overwhelming amount of evidence" that goes against common claims by historians that Hitler died in Berlin.

Williams claims he and Dunstan looked into recently de-classified documents and forensic tests, which shows findings inconsistent with popular assumption.

"We didn't want to re-write history, but the evidence we've discovered about the escape of Adolf Hitler is just too overwhelming to ignore," he said.

"There is no forensic evidence for his, or Eva Braun's deaths, and the stories from the eyewitnesses to their continued survival in Argentina are compelling."

'Grey Wolf: The Escape Of Adolf Hitler' claims the Fuhrer and his mistress Eva Braun were secretly flown out of Germany in April 1945 and taken to Argentina. The book claims Hitler lived in Argentina for 17 years and raised two daughters until his death in 1962.

The book also alleges US intelligence of conspiring to hide the truth about Hitler's escape.

"Stalin, Eisenhower and Hoover of the FBI all knew there was no proof of him dying in the bunker," Williams told Sky News, adding that the book's new findings prove the "Hitler" skull fragments held by the Russians are actually that of a young woman.

"It's difficult to understand why so much of the already published material we present in the book has been ignored over the years... It's only now that Argentina is once more a thriving democracy that the real stories are beginning to come out," he said.

The film Grey Wolf is currently in production and is expected to be released in January 2012.