Scientology's practices for dealing with those who have left the cult are well-known.

The process, known as Disconnection, involves essentially blanking former family members, lovers, friends and anyone who they believe to be a 'Supressive Person'. In some cases, it can go so far as harassment and even stalking.

Two parents in Las Vegas, Nevada, are now going to extreme lengths to reach their Scientologist children, whom they haven't spoken to in over two years. Phil and Willie Jones rented out a billboard space in Los Angeles' Echo Park near Dodgers Stadium. The parents, who are former Scientologists, attempted to erect a billboard near the Los Angeles Scientology Center on Hollywood Boulevard.

As Mr. Jones explained to THR, he's "pretty sure Scientology got to them on that. Then we found one on Hollywood Boulevard closer to La Brea, not far from where (Scientology leader) David Miscavige lives. We paid them in full, had the printing done, were one day from installation, and Scientology shut us down. They had one of their people call and offer to buy millions of dollars worth of billboard space all over the area just to shut us down."

Their two children, Mike (42) and Emily (38), are stilly deeply entrenched in the organisation after Phil's sister reported the parents to Scientology elders over doubts they had about the cult. The two were excommunicated immediately.

"If you leave Scientology and make any kind of critical remark at all, every Scientologist has to disconnect from you: family, friends, business. Because my wife and I were in it for so many years, our entire lives were surrounded by it. Literally overnight we were cut off from everyone, including our own children. There’s no recourse. You can’t call the kids up and talk about it. We’ve tried to phone, letters, we go to the building, and the security people come out: “You’re not welcome here.” We were at a loss as to what else to do, and that’s when we came up with the billboard. We wanted to make a statement: We want our families back. They’re holding them hostage."

Phil's son, Mike, was an aspiring musician and left home at 18 to travel to Los Angeles to make his name. However, he was then recruited by the Church and brought to their Celebrity Center in downtown Los Angeles. "They convinced him the music industry is insane and that he could only play guitar once the planet was “clear.” ... There are a lot of people who have developing careers who drop them when they join Scientology staff. The ones who have big careers - the Tom Cruises and John Travoltas of the world - they had their careers before Scientology."

The Church of Scientology has, of course, hit back at the Jones' claims, saying that "there is no fact checking with billboards. It is shameful that two people desperate for publicity would hook up with a reality TV producer to shamelessly exploit and harass their two adult children for money. It is equally despicable that these individuals would use a private family matter to promote anti-religious hate and bigotry and harm their kids."

The Jones admitted that they are working with a TV producer to document their story, however they were unable to talk any further about the documentary or what they're planning. Louis Theroux's documentary, My Scientology Movie, hasn't yet received a wide release - either online or through mainstream cinemas.