A week after announcing his separation from his wife, the author of a bestselling book that told an entire generation of young Christians not to date has made the shocking admission that he has abandoned the faith.

Joshua Harris, the pastor wrote the controversial I Kissed Dating Goodbye, dropped the bombshell in an Instagram post on Friday that he is no longer a Christian.

The post was intended as an appendix to the update about his separation posted to Instagram a week earlier in which he said he and his wife of 21 years, Shannon, had undergone some "significant changes" and decided to continue their life together "as friends". 

In Friday's post, he revealed that some more information had been "left out" of that announcement. 

"My heart is full of gratitude. I wish you could see all the messages people sent me after the announcement of my divorce. They are expressions of love though they are saddened or even strongly disapprove of the decision," he said. 

"I am learning that no group has the market cornered on grace. This week I've received grace from Christians, atheists, evangelicals, exvangelicals, straight people, LGBTQ people, and everyone in-between. Of course there have also been strong words of rebuke from religious people.

"While not always pleasant, I know they are seeking to love me. There have also been spiteful, hateful comments that angered and hurt me.

"The information that was left out of our announcement is that I have undergone a massive shift in regard to my faith in Jesus. The popular phrase for this is 'deconstruction,' the biblical phrase is 'falling away.' By all the measurements that I have for defining a Christian, I am not a Christian. Many people tell me that there is a different way to practise faith and I want to remain open to this, but I'm not there now." 

His announcement will shock many further still with its inclusion of an apology to the LGBTQ+ community for refusing to affirm their place in the church and marriage equality.

"Martin Luther said that the entire life of believers should be repentance. There's beauty in that sentiment regardless of your view of God," he continued.

"I have lived in repentance for the past several years — repenting of my self-righteousness, my fear-based approach to life, the teaching of my books, my views of women in the church, and my approach to parenting to name a few.

"But I specifically want to add to this list now: to the LGBTQ+ community, I want to say that I am sorry for the views that I taught in my books and as a pastor regarding sexuality.

"I regret standing against marriage equality, for not affirming you and your place in the church, and for any ways that my writing and speaking contributed to a culture of exclusion and bigotry. I hope you can forgive me." 

Harris then went on to say that, owing to its "flaws", I Kissed Dating Goodbye was to be discontinued. 

He has already apologised in the past for the main thrust of the book, published in 1997, which argued that dating was spiritually unhealthy and a "training ground for divorce". 

In Friday's post he said: "In light of the flaws I now see in I Kissed Dating Goodbye, I think it's best to discontinue its publication, as well other supplemental resources tied to it (this includes the two books I wrote after it whose content is similar)."