The Nazis hoped to develop an army of talking canines, according to an academic at Cardiff University who has written a book on the subject.

Dr Jan Bondeson claims that the Nazis believed dogs possessed almost human intelligence and created a "school" to develop their communication skills. Adolf Hitler and other senior officials were known for their love of dogs.

At the institution, opened in the 1930s near Hannover, head Margarethe Schmitt trained the animals to tap the letters of the alphabet, and instructed them in religion, politics and poetry.

The previously unknown story is detailed in Dr Bondeson's book, Amazing Dogs: A Cabinet of Canine Curiosities.

Dr Bondeson said that it was an "absolutely extraordinary" story. But he added that "There is no evidence it ever actually came to fruition".

In January it emerged that a Finnish dog who answered to the name Hitler and could make a Nazi salute was the subject of a high-level investigation by the Nazis in the 1940s.