New research has revealed a dramatic decline in the number of practising Christians in the US. 

The study by the Barna Group is based on the data from over 96,000 surveys conducted over the last 20 years looking at faith practice in the US. 

While 45% of Americans were practising Christians in 2000, today that figure stands at just a quarter. 

"Christianity in the United States has undergone dramatic change in the last few decades," Barna said. 

"In essence, the share of practicing Christians has nearly dropped in half since 2000." 

It identified as practising Christians those who "agree strongly that faith is very important in their lives and have attended church within the past month". 

Over the same period, the proportion of non-practising Christians has risen from 35% to 43%, while non-Christians have increased from 20% to 30%. 

Those identifying as atheist, agnostic or religious "nones" has nearly doubled in size between 2003 (11%) and 2018 (21%). 

Barna said the research painted a "nuanced portrait of people trying to figure out what faith means in the 21st century and the role of Christianity in their lives". 

Commenting on the findings, David Kinnaman, president of Barna, said: "A lot of religion research—even Barna's—tracks single factors, such as church attendance.

"But the 'practicing Christian' measure is unique in that it combines three variables: calling oneself a Christian, strongly prioritizing faith and regular church attendance.

"Because each of those three factors have declined over the last twenty years among all adults, the net effect shows the major reshuffling of Americans spiritual lives.

"Monthly, committed churchgoers are now about half as common as they were two decades ago. This shift has major repercussions for church leaders as there is increased struggle to attract and retain the active segment of churchgoers.

"While the decline of Christian engagement is real, the data remind us that one-quarter of the population qualifies as a practicing Christian. This represents more than 80 million adults—a level of churchgoing that is a statistical outlier among affluent and educated societies."