Church of Scientology officials have blasted former member Paul Haggis after his open letter to actress Leah Remini was published in The Hollywood Reporter.

The writer and director has become a vocal opponent of the church and its elders ever since he quit in 2009 after 35 years, and he wasted little time in attacking the organisation's alleged practice of shutting out non-Scientologists as part of a missive about Remini's recent departure from the faith.

Haggis offered his support to the actress, who he claims stood by him when he became an ex-Scientologist, despite church elders advising her to cut ties.

A church spokesman has since issued a scathing statement to media outlets, insisting the Oscar-winning filmmaker's open letter to Remini is nothing but a "transparent plug" for his upcoming movie.

The statement continues, "Mr. Haggis once again is exploiting his tenuous connection with Scientology to grab headlines. His statement that the organization anonymously comments negatively about those who leave the church is delusional and borders on paranoia.

"(He has) no firsthand knowledge about the Church of Scientology (and gets his information from) a small collection of unemployed bloggers living on the fringe of the Internet... Mr. Haggis has chosen to align himself with a small posse of lunatics with arrest records, who have acknowledged in depositions to being secretly on the payroll of the tabloids and who have admitted on national television to outright lying."