The Westminster Confession begins with a chapter on the doctrine of Scripture. And it does so for good reason: all other Christian doctrine depends on it. A sound view of Scripture will tend to produce sound doctrine in other areas. Likewise, a defective view of Scripture will tend toward heresy. The New Perspective on Paul theologians have a defective view of Scripture in at least two areas: they deny both the inerrancy and sufficiency of Scripture.
Early on in his book What Saint Paul Really Said, NT Wright makes known his low view of Scripture by ironically insinuating that he’s not sure what Saint Paul really said,
Most of what I say in this book focuses on material in the undisputed letters [of the Apostle Paul], particularly Romans, the two Corinthian letters, Galatians and Philippians. In addition, I regard Colossians as certainly by Paul, and Ephesians as far more likely to be by him than by an imitator. But nothing in my present argument hinges on this one way or the other. – What Saint Paul Really Said, p.8
When Wright says that he regards Ephesians, “as far more likely to by by him [Paul] than by an imitator, he is spaking the subtle language of unbelief, for the epistle begins, “Paul, an apostle of Jesus Christ by the will of God.” For a man with the correct view of Scripture, the authorship of Ephesians is not a question to be pondered, it is a truth to be believed.
Wright also shows evidence of basic epistemological confusion. While the word epistemology can sound rather intimidating, the idea it expresses is fairly simple. Epistemology is the study of how we know what we know. The proper Christian position on epistemology states that we know what we know because God has revealed it to us in his word. All truth is graciously given by God in his word, and apart from his word man can know nothing. The statements of all scientists, philosophers, historians and theologians are to be tested against Scripture. If they do not agree with the Bible, they are false.
But Wright doesn’t see it that way. For him and contrary to the Westminster Confession, the apocrypha are indeed of authority in the church. Wright writes,
Sanders’ major work on Paul is entitled Paul and Palestinian Judaism. The echo of Davies was deliberate; Davies was one of Sanders’ teachers, and Sanders saw himself as continuing his emphasis, though in various new ways. Instead of reading Paul simply against his rabbinic background, he sketched out a much broader canvas of Palestinian Judaism in Paul’s day, looking at the Dead Sea Scrolls (which of course were not available when Davis first wrote), the apocrypha and pseudepigrapha, the wisdom literature, and so on. His major point, to which all else is subservient, can be quite simply stated. Judaism in Paul’s day was not, as has regularly been supposed, a religion of legalistic works-righteousness. If we imagine that it was, and that Paul was attacking it as if it was, we will do great violence to it and to him. – What Saint Paul Really Said, pp. 18-19
The problem here is that Wright, along with his mentors Sanders and Davies, does not know what proves what. Wright erroneously believes that we use the Dead Sea Scrolls, the apocrypha and pseudepigrapha to interpret the Bible, when, in fact, it is the Bible that informs our understanding of these other documents. We do not use Second Temple Judaism to establish our understanding of the Bible, we use the Bible to establish our understanding of Second Temple Judaism.
John Robbins made the point that when philosophical (and theological) systems go wrong, they tend to go wrong at the very beginning. This is certainly the case with NT Wright and the other New Perspective on Paul writers. Their erroneous and unbiblical epistemology leads them to their erroneous and unbiblical doctrine of justification.
Lux Lucet 
Well said, the irony is that these men ask us to trust them while rejecting the texts of the NT.
While we negotiate our way closer to N.T. Wright’s “worldview”, he continues on with his agenda. I quote from his essay on justification in The Great Acquittal, ed Gavin Reid, 1980):
“Precisely because we believe in justification, we must get our view of the Church sorted out, and have done once and for all with the watery semi-Baptist theology which has been creeping into evangelical Anglicanism over the last decade or two.
Justification belongs with the covenant signs: baptism is the sacrament of entry into God’s people, the sign of regeneration, and thus faith, which follows and does not precede regeneration, need not precede baptism, though if it does not follow afterwards there will consequently be no justification.”
My concern here is not to refute the idea that future justification is a result of regeneration imparting righteousness, nor even to reject the idea of infant baptismal regeneration.
I am saying that, if we choose to be quiet now about the semantics of what to call “justification” and “imputation”, then it will be too late to call into question Wright’s assumption that the finished atoning work of Christ needs to be supplemented by “regeneration” as the atoning work of the Holy Spirit.
I certainly appreciate the urge not to correct folks when they don’t talk about “sanctification” in the way the Bible does. After all, what can we expect when the confessions themselves talk about “more and more” sanctification?
Nevertheless, the Biblical language about “sanctification” has much to say about the holiness of God and the nature of the gospel. For an excellent book on the “sanctification” topic, I recommend David Peterson’s Possessed By God (Eerdmans, 1995, New Studies in Biblical Theology)