An ex-Muslim who co-founded an advocacy group for people who have left their religion says there's not enough support for apostates in New Zealand, despite it being a "chilled country".

Imtiaz Shams has become a poster boy for apostates, the name given to those who have renounced their religious beliefs. Once a practicing Muslim, the UK-based entrepreneur now lives openly as an atheist, offering assistance to those who feel neglected since leaving their religion.

"If you speak to most ex-Muslims, or even ex-Jehovah's Witnesses, they will say the same thing: They will say, 'I didn't even know I could leave [my religion],' because they didn't know anyone else who left it," Mr Shams told RadioLIVE.

The co-founder of Faith To Faithless made an appearance at the Humanist International Conference held in Auckland over the weekend. He says while it was liberating coming clean to his family about renouncing Islam, it was also one of the most difficult things he's ever done.

"I was the only person out of 1.6 billion people to leave Islam - that's what was going on in my head," he said, discussing the backstory of his path to establishing the advocacy group, which calls on governments and civil society to do more to protect non-religious people facing discrimination.

He said it's important for people to understand that they're not alone in doubting their commitment to religion. The pressure some people face to embrace a particular belief system because of community pressure can have an impact on mental health, he says, so people need to know where they can go for support.