Below quote was taken from RAPPLER.com entitled "The Major Difference between the Catholic Church and the Iglesia ni Cristo" Item No. 6:
Apostate Church. The INC accuses the Catholic Church of “unfaithfulness” or apostasy. Citing the prophesy of Apostle Paul, the early Church strayed away from the teachings of Christ. They cite the words of St Paul, who said that after his death, “men will arise who will speak perverse things to draw away the disciples of Christ after them (Acts 20:30)." The INC also cites St Peter, who said that false prophets will preach heresies “denying the Master, the Lord Jesus Christ, by rejecting him as Head of the Church…and by rejecting His name.”
The INC believes the descriptions squarely fit the Catholic Church. “The Catholic Church denied the Lord Christ’s headship by putting Peter and the Popes in His stead. It rejected His name, Christ, by sporting such an unscriptural name as Roman Catholic Church.”
The Catholic Church however, counters that it “has been faithful at all times to the Revelation” amid erroneous teachings and persecutions. The martyrdom of early Christians in the first 3 centuries is proof of the fidelity of the Catholic Church to Christ’s teachings.
In the first place, if the Catholic Church committed apostasy, “why does the INC use the Holy Bible that was ratified by the same Church in the 4th century?”