that was allegedly written by Barnabas
, one of the disciples of Jesus
. It is known that there was such a gospel in existence within two hundred years of the death of Jesus
, and it is referred to by early Christian scholars like Iraneus
. However, after the Councils of Nicea
, this Gospel was not included in the canon
of the Bible. Furthermore, the Church
ordered that all other religious writing not included in the canon
. Anyone found possessing a non-canonical gospel was executed
Now, it is claimed that one copy of the Gospel of Barnabas was found in the library of the Pope and through a variety of factors finally reached its current place which is in the Hofbibliothek in Vienna. Whether this is true or not, is the subject of much debate. A translation into English is available on the Web (see below).
It's problematic for Christians because it advocates unitarianism, that is to say, that God is one and one only, rather than trinitarianism, that is to say that God is the Father, the Son and the Holy Spirit. It also disagrees with the idea that Jesus is God, rather it advocates that Jesus is a prophet. This tends to cloud the issue of its authenticity or falsehood -- since it contradicts Christian dogma. However, most Christians don't realise that early in the history of Christianity, there was a raging debate over the divinity of Jesus.
More info (appearing to be relatively objective) can be found at: http://ironbark.bendigo.latrobe.edu.au/~blackhir/Entry.html