A startling number of Christians do not see anything wrong with sex outside marriage, according to new research by Pew.
Over half (57%) said sex between unmarried adults in a committed relationship was sometimes or always acceptable.
Support was highest among mainline Protestants (67%), followed by Catholics (64%), Black Protestants (57%) and evangelical Protestants (46%).
When it came to casual sex - defined in the survey as sex between consenting adults not in a committed romantic relationship - half said this was sometimes or always acceptable.
Evangelical Protestants were far less likely to agree with this view (36%), compared to Catholics (62%), black Protestants (56%) and mainline Protestants (54%).
Regular churchgoers - defined as those who attend church at least monthly - were less likely (46%) than those who attend less often (74%) to say that pre-marital sex in a committed relationship was always or sometimes acceptable.
Approval of casual sex soared to 84% among the religiously unaffiliated, 94% among atheists and 95% of agnostics.
There was less acceptance among Christians about other behaviours, with just over a third saying that it was sometimes or always acceptable for consenting adults to exchange sexually explicit images of themselves.
While only 12% of those who attend church at least monthly believe sex on the first date is always or sometimes acceptable, this rose to 38% among those who attend less often.