The Christian Church is "moments away" from accepting gay marriage, according to author and former megachurch pastor Rob Bell.

Speaking to TV host Oprah Winfrey on her Super Soul Sunday programme, Bell – who has fallen out of favour with many evangelicals in the US because of his perceived theological unorthodoxy – said that it was "inevitable" that churches would change their position.

Bell and his wife Kristen were speaking about their book The Zimzum of Love: A new way of understanding marriage. The segment begins with Kristen Bell reading from the book and saying: "Marriage, gay and straight, is a gift to the world, because the world needs more, not less, love, fidelity, commitment, devotion and sacrifice."

Asked why the couple chose to address gay marriage specifically in the book, Bell said: "One of the oldest aches in the bones of humanity is loneliness. Loneliness is not good for the world. Whoever you are, gay or straight, it is totally normal, natural and healthy to want someone to go through life with. It's central to our humanity. We want someone to go on the journey with."

When Winfrey asked, "When is the Church going to get that?" Bell said: "Lots of people are already there. We think it's inevitable and we're moments away from the church accepting it."

He added: "I think culture is already there and the Church will continue to be even more irrelevant when it quotes letters from 2,000 years ago as their best defense, when you have in front of you flesh-and-blood people who are your brothers and sisters, and aunts and uncles, and co-workers and neighbours, and they love each other and just want to go through life with someone."

However, Kristen Bell said: "I think there are a lot of people who as they see culture moving, their response is to dig in deeper and hold their ground."