>> because i think they believe it is a way to somehow get at david miscavige. >> he is so caring. >> reporter: the church sent us 126 interviews they recorded with their parishioners praising their leader. >> he has the heart of a lion. >> dedicated to our religion. >> mr. miscavige is an amazing person. >> i will love him forever. >> reporter: ron's testimony is different. he says by the late 2000s, the crushing workload, the discipline and lack of sleep on the base becomes unbearable. the church rejects those claims, telling us long and hard hours and a restrictive lifestyle are part of the mission sea org members sign on for in those billion-year contracts. >> they're very proud of what they may work really long hours, even longer than we do, but they enjoy it. >> reporter: as for ron -- >> he was working with first class musicians in one of the best studios in the world. he had nothing to complain about. >> reporter: to prove it, the church has provided "20/20" with pictures of ron at leisure, enjoying fancy birthday meals provided by his son and even getting a car for his birthd

>> i know it. >> reporter: at age 16 david miscavige joins the see organization, the religious order of the church and develops a close relationship with church founder, l ron hub bard. in 1986 when hub ard days, david takes control taking chairman of the board. by this time, david's father ron has also joined. quickly ron says he noticed his son's sharp edged new management stage. >> he's tearing my apart backstage cursing, yelling, screaming at me. >> reporter: one night at a church event where ron is performing he says david gives him an extended tongue lashing with other people looking on. when he's scream agent you do you ever think i changed this guy's diapers? >> no kidding. of course i did. and that isn't the only time it happens. >> reporter: and he says life for members deteriorates. he describes crushing workloads, restrictive rules, a rigid lifestyle and a lack of sleep. >> as time went on, it slowly went downhill and got worse and worse. >> reporter: the church rejects the claims telling us long and hard hours and a restrictive lifestyle are part of the lifestyle they sig

they come in a new book, written by david miscavige's own father, after he broke away from scientology and from his own son. abc's dan harris, with the father and the family now ripped in two. >> reporter: ron miscavige, now breaking ranks and publicly criticizing his own son, the powerful leader of the church of scientology, david miscavige. >> if you are a scientologist, you are one of the relative few that hold the answers in your possession that all humankind depend upon. >> reporter: ron was in the church for decades, but has now left and written a book, which he discusses in an exclusive interview with abc news. you have written a whole book about your son, and you've called the book "ruthless." >> yeah. >> reporter: that's a pretty damning charge to level against your own child. >> he wasn't always that way. when he was a kid, i am telling you, he was a lovable kid. >> reporter: a lovable kid who, according to his dad, let the power of being at the helm of this wealthy, celebrity-studded church, go to his head. >> and i say to you sir, c.o.b, we are lucky to have you and thank y

cruise celebrated his 41st birthday, the man next to him was the undisputed leader of scientology, david miscavige. but playing the horn, ron miscavige, his dad. what's the relationship? >> tom cruise thinks that david is the top spiritual being on the planet. >> reporter: he's speaking out about why he decided to leave the church, and write a book about his own son called "ruthless." >> power tends to corrupt. that taste of power, i think, is what changed david. >> reporter: he said one night, david gave him an extended tongue lashing with other scientists look on. >> he's backstage, tearing me apart for 55 minutes. cursing, screaming, yelling at me. >> reporter: he says his life in the sea org became unbearable because of crushing workloads and little sleep. the church is pushing back. >> they may work hard, but they enjoy it. >> reporter: and letters from ron's former band mates calling him lazy and a disgusting pig. and ron said if he was that bad, he would have never been put front and center with tom cruise. >>> and later tonight, on "20/20," more on the story, 10:00 p.m. tonight right here.

cruise celebrated his 42nd birthday, the man next to him was the undisputed leader of scientology, david miscavige. but look in the background. the older gentleman playing the horn? that's ron miscavige, david's dad. who's now going public. what's the relationship? >> tom cruise thinks that david is the top spiritual being on the planet. they're, like, the best of buddies. >> reporter: he's speaking out about why he decided to leave the church, and write a book about his own son called "ruthless." >> power tends to corrupt. and absolute power corrupts absolutely. that taste of power, i think, is what changed david. >> reporter: he said he experienced his son's temper one night. david gave him an extended tongue lashing with other scientologists looking on. >> he's backstage, tearing me apart verbally for 55 minutes. cursing, screaming, yelling at me. >> reporter: he says his life in the sea org became unbearable over time because of crushing workloads a rigid lifestyle, and little sleep. the church is pushing back. >> they may work hard. they may work really long hours, even more than we do, but t

you, c.o.b., we are lucky to have you and thank you very much. >> reporter: when word hit that david miscavige's own father, the now 82-year-old ron miscavige had left the church after decades of service, leah remini says it spread like wildfire. >> i tracked him down. i called him and i offered my support because i know he must i just wanted him to know that we were willing to take them in >> that's a big offer. what made you feel motivated to do that. >> because there is no place for them to go unless they have family, which is very rare outside of the church. >> did you encourage him at all to go public with his story? >> yes, i mean i immediately said that he should write a book because his story is important. >> reporter: now ron miscavige has written a book and he's speaking about it in an exclusive interview that will air on abc's "20/20" on friday night. you have written a whole book about your son and you've called the book "ruthless". >> yes. >> it is a pretty damning charge to level against your child in he wasn't always that way. when he was a kid, i am telling you, he was a lovable

david miscavige. >> you are one of the relative few that hold the answers in your possession that allnd upon. >> reporter: ron was in the church for decadeses but left and written a book which he discusses in an interview with abc news. >> you have written a whole book about your son and you called the book "ruthless." >> yeah. >> it's a pretty damning charge to level against your own child. >> he wasn't always that way. when he was a kid, i am telling you, he was a loveable kid. >> reporter: a loveable kid who according to his dad, let the power of being at the helm of this wealthy celebrity studded church go to his head. >> i say to you sir, we are lucky to have you and thank you attacking the book arguing it was co-authored by a noted critic of church management and is laden with outright lies. >> it is not a memoir. it's in my view a literary forgery. >> he has a right to tell his story but leah remini. >> you are unbelievable. >> reporter: the former star of the king of queens" who can herself was criticized by scientology after she quit the church and wrote a book is, going to b

that older gentleman playing the horn, that's ron miscavige, david's dad, who now much to the chagrin decided to step out and play so solo. >> what's the relationship between your son and tom cruise? >> tom cruise thinks that david is the top spiritual being on this planet. >> the top spiritual being on the planet. >> ron miscavige now 80 is now speaking out about why he decided to leave the church and write a book about his own son called "ruthless". >> power tends to corrupt, and absolute power corrupts absolutely. that taste of power i think is what changed david. >> reporter: ron spent threely three decades working in the religious order of the church where he says he witnesses hi son's volcanic temper. >> david is backstage literally tearing me apart verbally for 55 minutes, cursing, yelling, screaming at me. >> reporter: for six years ron lived on a sprawling steintology base in hemmette, california, known as gold. >> it got worse and worse and worse. >> reporter: ron blame his son for what he calls an intensely stressful atmosphere at the base and says overtime the crushing wor

david miscavige hasn't spoken to since 1992 but now his father is speaking out against him. >> you called

david miscavige hasn't spoken to since 1992 but now his father is speaking out against him. >> you callednight former signtologists complain their families won't

david miscavige hasn't spoken to since 1992 but now his father is speaking out against him. >> you called the book ruthless. >> yeah. >> that's a damming charge against your child. >> he wasn't always that child. >> ron miscavige said it's cost his relationships with his own daughters and tonight former signtologists complain their families won't speak to them and

that older gentleman playing the horn, that's ron miscavige, david's dad who now much to the chagrinch has decided to step out and play solo. what's the relationship between your son and tom cruise. >> tom cruise thinks that david is the top spirit cal being on this planet. >> the top spiritual being on the planet. >> they're like the best of buddies. >> reporter: in an exclusive interview ron miscavige now 0 speaking out about why he decided to leave the church and write a book about his own son called "ruthless." >> power tends to corrupt and absolute power corrupts absolutely. that taste of power i think is what changed david. >> reporter: ron spent nearly three decades working in the seaorg, the religious order of the church where he witnessed his son's volcanic temper. >> david is backstage literally tearing me apart verbally for 55 minutes cursing, yelling, screaming at me. >> reporter: for six years ron lived on a sprawling sinai peninsula base in california known as gold. >> it got worse and worse and worse. >> reporter: ron blames his son for what he calls an intensely stres