Only a quarter of US evangelicals believe that abortion should be illegal in all cases, a new study has found. 

A third of self-identifying evangelicals surveyed by pro-life group Save the Storks agreed that abortion should be illegal in most cases, while 15% said it should be legal in all cases and just over a quarter (27%) supported it being legal in most cases.

The poll of 1,000 US adults aged 18 to 69 revealed that mainline Protestants (18%) and Catholics (16%) were less likely than evangelicals to support a blanket ban on abortion. Just under a third of Protestants (31%) said they believed abortion should be illegal in most cases, slightly higher than Catholics holding the same view (28%).

Even among those who self-identified as pro-life, only a third (34%) of respondents said that abortion should be illegal in all cases, while over half (52%) said it should be illegal in most cases.

A quarter of all respondents described themselves as "pro-life", far lower than the 40% identifying as "pro-choice", although over a quarter (29%) said they were "neither or a mix of both". 

Of the respondents identifying as evangelical, nearly half (47%) identified as pro-life, far higher than a third of mainline Protestants and a quarter (27%) of Catholics. 

Only 18% of evangelicals said they were pro-choice, compared to a third of Catholics (34%) and a similar proportion of mainline Protestants (36%). 

Those who identified as "non-religious" were far more likely to describe themselves as pro-choice (53%), with only 14% saying they were pro-life. 

The survey also shed light on perceptions of when life begins, with evangelicals (42%) being far more likely than Catholics (31%), mainline Protestants (34%) and non-religious respondents (21%) to say that a fetus is a living being at the point of conception. 

Catholics (38%) were the most likely, though, to believe that a fetus becomes a living being from the first heartbeat, followed by evangelicals (36%) and mainline Protestants (30%). 

Even among non-religious respondents, over half (55%) agreed that a fetus can be regarded as a living being at the point when the heartbeat can be detected or earlier.

Dr Karysse Trandem, spokesperson for Save the Storks, said: "There's a disconnect in our culture right now.

"The majority of Americans believe that life begins at or before the heartbeat, but the majority of evangelicals and Catholics identify as pro-choice."

Save the Storks President Paul Isaacs said: "We hope this research is the beginning of an honest dialogue among Christians.

"We are going to have to work harder to equip the next generation of Christians to have a more life-affirming ethic on this issue."