The number of people who don't identify with any denomination in the US has increased by 30 per cent since the Cold War years, according to a new survey. 

New data released by the US Religion Census has found at least 9,000 churches which do not identify with traditional denominations have surged in the last decade. 

The increase takes the number of non-deminational churches in 2010 from 35,496 to 44,319 in 2020. 

This means that, in total, there are now 3.4 million more people in non-denominational churches than there are Southern Baptist Convention congregations, one of the largest denominations in the US. 

The report also found the number of people adhering to Southern Baptist and the United Methodist Church, has decreased by two million in comparison to those adherent to non-denominational churches, which has increased by nearly nine million. 

"Denominational brands have weakened, and divisions have increased over issues such as female clergy or sexual orientation. This likely led some adherents to seek or even start new, non-denominational churches," Scott Thumma, director of the Hartford Institute for Religion Research, who counted independent churches for the study, said in a statement.

The Southern Baptist Convention, the Assemblies of God, the Presbyterian Church in America, the Church of the Nazarene and the Evangelical Free Church have all seen a modest growth in congregations across the country.

Among other denominations, the Anglican Church in the US declined from 913 churches to 873.

The data also found the number of non-Christian bodies has continued to grow in the US citing the number of Muslims as an example of this trend - there are 1.9 million more Muslims than ten years ago.