People's sex lives improve dramatically after leaving religion, researchers in the US have found.

"Atheists have far better sex lives than religious people who are plagued with guilt during intercourse and for weeks afterwards," the Daily Mail reported.

"A study discovered that non-believers are more willing to discuss sexual fantasies and are more satisfied with their experiences.

"Both groups of people admitted that they carried out the same activities such as masturbation, watching pornography, having oral sex and pursuing affairs.

"But followers of religion did not enjoy the experiences as much due to the stigma created by their belief systems, the study found. It left them with intense feelings of regret after they had climaxed."

The Sex and Secularism study of more than 14,500 people looked at the links between religion and sex.

Questions included "How do religious parents educate their children compared to non-religious parents? When do people start sex and is there a difference based on religious training? How does religious guilt play into the whole equation?"

The survey was led by Recovering from Religion founder and psychologist Darrel Ray and Amanda Brown from Kansas University.

"All of the people who were questioned were found to have sex around the same number of times a week. They also became sexually active at similar ages," The Mail said.

"Strict religions such as Mormons ranked highest on the scale of sexual guilt. Their average score was 8.19 out of 10. They were followed closely behind by Jehovah's Witness, Pentecostal, Seventh Day Adventist, and Baptist.

"Catholics rated their levels of sexual guilt at 6.34 while Lutherans came slightly lower at 5.88.

"In contrast, atheists and agnostics ranked at 4.71 and 4.81 respectively."

The findings dispelled beliefs that feelings of guilt could continue to plague people after leaving their religion.

"We did think that religion would have residual effects in people after they left but our data did not show this," Mr Ray told alternet.org.

"That was a very pleasant surprise. The vast majority seem to shake it off and get on with their sexual lives pretty well.

"Our data shows that people feel very guilty about their sexual behaviour when they are religious, but that does not stop them, it just makes them feel bad.

"Of course, they have to return to their religion to get forgiveness. It's like the church gives you the disease, then offers you a fake cure."

Mr Ray was raised in a fundamentalist Christian home, but left religion in his 30s.

He founded Recovering from Religion in 2009 to help people who needed a support system to help them deal with the aftermath of leaving religion.