Mr Powell, who was Professor of Greek at Sydney University by the age of 25, announces his conclusions in the notes and preface to a new translation he has made of St Matthew's gospel, which will be published by Yale University Press next month.
Some of his claims are accepted as possible, if improbable, by other experts. But his claim that the crucifixion never happened was dismissed as wildly eccentric by experts the Independent spoke to.
Mr Powell grounds his closely argued case on a belief that Matthew's is the first of the four gospels to have been written, and that Mark and Luke derive from it.
Most scholars of all denominations believe that the terser Gospel of Mark was the first to be written, and that the authors of Matthew and Luke drew from it, as well as from another source, now lost, known only as 'Q'.
However, Mr Powell sees Matthew's gospel itself as the product of several revisions. 'The most significant feature of Matthew is the coexistence in it of passages, one of which is an alternative to, or a duplicate of, the other.
'The alternatives cannot have been composed to stand side by side in the same book with the passages to which they were alternative. It follows that they must have been introduced later into the underlying book from the work for which they were composed; and as that process cannot have been accidental or unintentional it must represent deliberate acceptance or conflation of contradictory material.'
Starting from this premise, he sets out to disinter the original book, to which the contradictory material was added. 'It was a document consisting exclusively of the words and actions of Jesus and preoccupied with establishing and demonstrating his identity as the 'son of God'; he is explicitly so born; and he is put to death by stoning, convicted by the Jewish establishment of the blasphemy of allowing himself to be called 'the son of God' .'
One of the Church of England's leading scholars, the Dean of Lichfield, Dr Tom Wright, dismissed this hypothesis: 'The crucifixion of Jesus of Nazareth is one of the most securely attested events in the ancient world. To attempt to overturn it on the basis of a hypothetical document which was suppressed 2,000 years ago and then allegedly recovered by someone reading the original text without the assistance of any other scholars simply beggars belief,' said Dr Wright.
A spokesman for the Catholic media office was more succinct. 'If Mr Powell is right, we're going to have to make a lot of changes to church architecture.'
Powell's Christian beliefs, page 3