A top academic has defended a five-year study that found conservative churches grow faster than liberal ones. 

The paper, published in December's Review of Religious Research, found that churches that relied on a more literal reading of the Bible and a certain belief in hell were more likely to grow than others.

The researchers interviewed 2,225 churchgoers in 22 congregations in Ontario, Canada, as well as 29 clergy.

They found that the churches that were growing were those that "held more firmly to the traditional beliefs of Christianity and were more diligent in things like prayer and Bible reading".

Now lead researcher David Haskell, writing in the Washington Post, has issued a riposte to the countering argument used in defence of liberals – that it is the strength of belief, not the specific content of faith, that causes growth.

In this scenario, liberal pastors are just as likely as conservative pastors to experience church growth, provided they are firm and clear in their religious convictions.

Haskell says his study shows this is not actually the case. "Different beliefs, though equally strong, produce different outcomes," he says.

Haskell, professor of religion and culture at Wilfrid Laurier University, notes in his latest comment that mainline Protestant churches in the US are losing about one million members annually. "Fewer members not only means fewer souls saved, a frightening thought for some clergy members, but also less income for churches, further ensuring their decline."

Episcopal bishop John Shelby Spong, author of Why Christianity Must Change or Die, was among those who argued that churches should become more liberal in order to survive.

But Haskell says his research was definitive: "Conservative Protestant theology, with its more literal view of the Bible, is a significant predictor of church growth while liberal theology leads to decline."

He concludes: "If it's any consolation, when it comes to growth in mainline churches, Spong and other liberals are right to claim that Christianity must change or die. They just get the direction of the change wrong."