What official statements represent Christianity's position on the Gospel of Barnabas? The Gospel of Barnabas is a text that has turned up in the form of 16th century manuscripts in Italian and Spanish. The text claims to be the witness of Jesus' disciple Barnabas, however its content runs quite contrary to Christian doctrine in every major tradition that I know of.

Secular media, however, loves to trumpet its claims and it periodically makes the rounds in pop culture. Sometimes it is touted as an alternate rendition of the Biblical New Testament account (either to be considered the true one if you discount the NT or a bogus one if you trust it). While the media doesn't tend to cover this, most scholars recognize that it's teachings are hugely divergent from those of Christianity.

What Christian traditions have come down with official statements with direct bearing on this text either approving or rejecting it's claims? What secondary positions (creeds, confessions, etc) could be shown to directly address it? Have any Christian traditions ever given it's teaching any authority?
This is an English translation of the Decretum Gelasianum de Libris Recipendis et Non Recipiendts.  The Decretum Gelasianum was issued by Pope Gelasius [Pope of Rome 492-96].

One of the apocryphum mentioned is "the Gospel in the name of Barnabas".

Now, the document floating around in the present day is probably a 16th century writing, just based on content analysis.  However, a version that existed in the 5th century was rejected by the Roman Catholic church as apocryphum.