America's loss of religion will dramatically accelerate over the next 20 years and those with no faith will become the largest 'religious' grouping.

This is according to Allen Downey, a professor of computer science at Olin College, who used historical data from the General Social Survey (GSS) to make predictions about the future of religious belief in the US.

While America has 'defied gravity' in that it has maintained high levels of religiosity as it became more modern, Downey says 'secularisation in the US will accelerate in the 20 years'.

In a blog post offering an extended version of research first published in the Scientific American he wrote: 'The fraction of people with no religious affiliation has increased from less than 10% in the 1990s to more than 20% now. This increase will accelerate, overtaking Catholicism in the next few years, and probably replacing Protestantism as the largest religious affiliation within 20 years.'

Not only that but the strength of belief from those with faith will also decline as those who believe the Bible is the actual word of God to be taken literally is set to decline as those who view the Bible as a series of legends will increase.

Downey makes clear this research could just reflect a loosening of the stigma of being viewed an atheist in the US rather than actual views changes.

'Due to social desirability bias we can't be sure what part of these trends is due to actual changes in belief, and how much might be the result of weakening stigmas against apostasy and atheism,' he writes. 'Regardless, these results indicate changes in what people say they believe.'