Since everyone seems to have taken the Daily Mail as a reliable source, I feel compelled to cite Wikipedia for a bit more information on this fraud....
Some readers have noted that the Gospel of Barnabas contains a number of apparent anachronisms and historical incongruities:
It has Jesus sailing across the Sea of Galilee to Nazareth – which is actually inland; and from thence going "up" to Capernaum – which is actually on the lakeside (chapters 20-21); though this is contested by Blackhirst, who says that the traditional location of Nazareth is itself questionable.
Jesus is said to have been born during the rule of Pontius Pilate, which began after the year 26.
Barnabas appears not to realize that "Christ" and "Messiah" are synonyms, "Christ" (khristos) being a Greek translation of the word messiah (mashiach), both having the meaning of "anointed". The Gospel of Barnabas thus errs in describing Jesus as "Jesus Christ" (lit. "Messiah Jesus" in Greek), yet claiming that 'Jesus confessed and said the truth, "I am not the Messiah"' (ch. 42).
There is reference to a jubilee which is to be held every hundred years (Chapter 82), rather than every fifty years as described in Leviticus: 25. This anachronism appears to link the Gospel of Barnabas to the declaration of a Holy Year in 1300 by Pope Boniface VIII; a Jubilee which he then decreed should be repeated every hundred years. In 1343 the interval between Holy Years was reduced by Pope Clement VI to fifty years.
Adam and Eve eat an apple (ch. 40); whereas the traditional association of the Fruit of the Tree of the Knowledge of Good and Evil (Book of Genesis 2:9,17; 3:5) with the apple rests on the translation of the Hebrew Bible into Latin, where both 'apple' and 'evil' are rendered as 'malum'.
The Gospel talks of wine being stored in wooden casks (chapter 152). Wooden casks were a characteristic of Gaul and Northern Italy, and were not commonly used for wine in the Roman empire until after 300 CE; whereas wine in 1st century Palestine was always stored in wineskins and jars (amphorae). The Pedunculate or English Oak Quercus robur does not grow in Palestine; and the wood of other species is not sufficiently airtight to be used in wine casks,
In Chapter 91, the "Forty Days" is referred to as an annual fast. This corresponds to the Christian tradition of fasting for forty days in Lent; a practice that is not witnessed earlier than the Council of Nicaea (325). Nor is there a forty days' fast in Judaism of the period (see Mishnah Tractate Ta'anit, "Days of Fasting").
Where the Gospel of Barnabas includes quotations from the Old Testament, these correspond to readings as found in the Latin Vulgate; rather than as found in either the Greek Septuagint, or the Hebrew Masoretic Text. However, it should be noted that the Latin Vulgate translation was a work that St. Jerome began in 382 AD, centuries after the death of Barnabas.
In Chapter 54 it says: "For he would get in change a piece of gold must have sixty mites" (Italian minuti). In the New Testament period, the only golden coin, the aureus, was worth approximately 3,200 of the smallest bronze coin, the lepton (translated into Latin as minuti); while the Roman standard silver coin, the denarius, was worth 128 leptons. The rate of exchange of 1:60 implied in the Gospel of Barnabas was, however, a commonplace of late medieval interpretation of the counterpart passage in the canonical Gospels (Mark 12:42), arising from the standard medieval understanding of minuti as meaning 'a sixtieth part'.
Chapter 91 records three contending Jewish armies 200,000 strong at Mizpeh, totaling 600,000 men, at a time when the Roman army across the entire Empire had a total strength estimated as 300,000.
In Chapter 119 Jesus instances sugar and gold as substances of equivalent rarity and value. Although the properties of sugar had been known in India in antiquity, it was not traded as a sweetener until industrial-scale production developed in the 6th century. From the 11th to 15th centuries, the sugar trade into Europe was an Arab monopoly, and its value was often compared with gold. From the mid 15th century, however, large scale sugar estates were established in the Canary Islands and the Azores, and sugar, although still a luxury item, ceased to be exceptionally rare.
Despite the inaccuracies above, one can see that (a) the writer of the manuscript is of an Italian origin, (b) it is possible that the revisions from time to time were based on the teaching of the Gospel of Barnabas.
It's obviously written by Muslims who fabricated a "Gospel" to prop up their belief.