In a rare interview Boston-based Peter Murphy has spoken about the anguish he suffered when he found out the disgraced cleric wanted to have him adopted.

Twenty years ago his mother, Annie Murphy, caused outrage in the more conservative and Catholic Church-dominated Ireland of the time when she appeared as a guest on The Late Late Show and revealed she’d had an affair with Casey in the Seventies.

Casey, who was ordained Bishop of Galway in 1976, quit his post in 1992 and fled the country after details of his 18-month affair with the American divorcee emerged, together with the bombshell revelation that that they had had a child together.

In a new TV interview to be aired on Irish TV next week, Murphy told of his belief and satisfaction that has own birth acted as a “catalyst” for the eventual separation between Church and State.

He also revealed he wanted to “deck” broadcaster Gay Byrne for the way he spoke to his mother during the famous Late Late Show interview.

In his parting words to Annie Murphy, which triggered an outburst of applause from the TV audience, Byrne had said: “I hope his son will be half the man his father was.”

But, recalling how offended he felt at the time, Murphy said: “I am an only child to a single mother. I wanted to fly across and deck him. The first thing you want to do is drop him.”

Murphy also admitted he “freaked out” and was “a blistering mess” after meeting up with his father for the first time in a lawyer’s office in the early 90s – a couple of years before his mother – who is now 64 and living in California – went public with her story.

He recalled: “We were in a law office. My absolute memory of the event isn’t word for word, but it was me trying to engage him and him having really no interest in engaging back with me.

“It was so emotional, I remember it affected me really badly, I freaked out.

“I ran out of the room and went down the elevator and I was a blithering mess.”

Murphy, who now works as a salesman for an electronics company in Boston, also told of his enduring anger at Bishop Casey’s attempts to persuade his secret lover to have him adopted – even before his birth on July 31, 1974.

He said: “Trying to get me into adoption before I was born and how he instantly changed tune when my existence was alerted…like woah [this] dirty little secret needs to go somewhere.”

He added: “Whether he thought he made a mistake or not, I was the example of the end to all his hard work.”

Casey, now 86, returned to Ireland in 2006 and is now in a nursing home.

The interview is the latest in the series ‘Print and be Damned’ and airs on Irish TV station TV3 at 9pm next Thursday (Aug 8).