Farro told Common Revolt, a music website, this week, "Paramore claimed to be a Christian band, and then wrote those lyrics. It contradicts your faith."
He was speaking about the lyrics to the song "Careful," which include "the truth never set me free, so I did it myself."
According to Farro, Paramore's lead singer, Hayley Williams, "always said it was meant to be 'your truth never set me free.'"
"But you know, if it was meant to be that, then why was it changed? It's kind of a sorry excuse. It bummed me out, and obviously one of many reasons me and Zac walked away."
Paramore is a chart-topping rock band that has been nominated for three Grammys. While the Farro brothers were two founding members of the band, they decided to split from the five-member group. An announcement in December revealed that the two made the decision to leave a few months prior.
"None of us were really shocked. For the last year it hasn't seemed as if they wanted to be around anymore," Paramore said in its statement at the time.
As Farro mentioned, faith likely played a big role. Williams and bassist Jeremy Davis said in an interview with Fuse.tv earlier this year that they used to attend church every week but as soon as they started touring and playing shows on Sundays, their churchgoing was no longer regular.
"It's really weird how much everything changed once we started touring," Williams said. "I remember spending one Easter Sunday at Hooters … and it's just because your life on tour, you don't remember what day it is."
She maintained that Jesus and God is still important to her and the rest of the band and that they pray before every show.
In terms of infusing her faith into her songs, Williams indicated that she avoided that.
"It's not our job to teach people," she told Fuse.tv. "I think that what we believe will most likely always shape our opinions and our thoughts but it's not our goal to write that down and spread it for everyone to learn from.
"It's not my job to tell them if it's right or not … we can only deal with our own hearts."
Farro revealed in a separate interview with MTV that he and Williams disagreed on a lot of things. But he doesn't want to turn the band breakup into a huge drama or dwell on it and stressed that he and his brother are focusing on the future.
The Farro brothers are currently working on a new band, Novel American. While the band is in its early stages, they hope to come out with an EP soon.
"This time next year I think it'll look like us touring, hopefully supporting an EP. I'm hoping that we'll maybe even have a full length out by then," said Josh Farro.
Putting the past behind, he also stressed to Common Revolt, "We couldn't be happier where we are right now."