The tales date from between 300BC and AD600. They include stories about biblical characters, wise sayings, poetry and prophecies.

Researchers at the University of St Andrews have launched a project to translate into English the texts, some written in the name of Old Testament characters such as Moses and Enoch.

James Davila and Prof Richard Bauckham, of the School of Divinity, said the documents showed that ordinary Jews and Christians wanted to know more about biblical characters.

The ancient tracts are similar to biblical texts, but written by unknown authors.

"Some of these books are surprisingly unorthodox," said Dr Davila. "We learn, for example, that some Christians and Jews enjoyed stories about miscegenation between angels and humans."

The 50 documents to be translated have been discovered in different locations.

They include the Testament of Adam, Apocalypse of the Seven Heavens and Visions of Heaven and Hell.

One book, Signs of the Judgment, popular in medieval times, contains a set of cosmic signs supposedly revealing when the Day of Judgment is approaching.