This, of course, is not an accurate statement when one actually goes to the Scriptures and reads for himself the recorded account as to what actually happened at that Church council. This is a perfect example of why God provided us with His inspired, written Word, and according to divine wisdom did not rely upon the fallible memory of men to preserve His truth down to this present generation. Men who could innocently be mistaken or consciously contort or misrepresent the accounts in order to conform them to their own religious slant. The Scriptures were given to us that we may test the words and traditions of men (2 Tim. 3:16).
The question at the council was whether or not Gentile believers needed to be circumcised. In other words, need they submit to Judaism and the Law of Moses? Peter stood up and testified of his experience with Cornelius and his family and friends, how after hearing the gospel of Jesus Christ they believed and were given the Holy Spirit, as did they on the day of Pentecost, cleansing their hearts by faith (Acts 15:7-11; Acts 10-11). Paul and Barnabas then related how God performed signs and wonders among the Gentiles through them, apart from their being circumcised (i.e., submitting to the Mosaic Law). The final word came not from Paul, Barnabas, and not even Peter, but James, the brother of the Lord, not even one of the apostles. And his authority was written Scripture itself (Acts 15:15). He quoted the prophet Amos where in the future Millennial Kingdom (“after” this Church age) Gentiles will be ushered in as Gentiles (Acts 15:16-18; cf. Amos 9:11-12). And so it is during this Church age, as well. The Gentiles are brought into the Church (the Body of Christ) by faith alone.
This conclusion by James, was backed up by both Peter and Paul (Apostles) and is consistent with all New Testament teachings - our final authority.
Yes, the Church existed prior the New Testament. Just as Israel existed prior to the Law of Moses. But as the Law of Moses (God’s written Word) became Israel’s divine authority, the New Testament Scriptures (God’s written Word) became the divine authority for the Church. The Church has no higher authority than God’s written Word.