One of the major reasons why there was the Protestant split with the Catholic church was over the nature of justification. Luther and others argued for justification by faith alone, while the Catholic Church reiterated its commitment to justification by faith and works. I affirm justification by faith alone, though I know that Catholics understand justification a little differently (they do not make a sharp distinction between justification and sanctification), so it is an oversimplification to accuse the Catholic Church of teaching a gross works-righteousness.
Protestants are armed with many texts, such as Eph. 2:8-9: “For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works, so that no one may boast” (NASB). However, while the Reformers harped on passages like this, the Catholic Church had James 2:14-26, which includes the famous phrase, “Faith without works is dead” (2:26b). Due to this and other issues, Luther had doubts about the book of James and is famous for calling it “an epistle of straw.” While he seems to have retracted that statement and eventually accepted a harmonization between it and the Pauline epistles, he clearly favored the latter.
Protestants have since readily explained that while salvation is by faith alone, a true faith will always produce good works if given the time. This is often stated, “Salvation is by faith alone, but faith is never alone.” This is why Paul states after Eph. 2:8-9 in v. 10, “For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand so that we would walk in them.” However, while this seems straightforward, it turns out that this is not so easy to see in James 2:14-26 on face value. James says in 2:24: “You see that a man is justified by works and not by faith alone,” which a Catholic might say is about as clear a repudiation of justification by faith alone as you can ask for. Thus, Protestants should give a careful account of this passage, just as Catholics need to deal carefully with passages like Ephesians 2. I hope to do so below, though I will neglect giving background information for space considerations.