Pope Francis may have gotten the respect of the Christian world and other religious groups for his stand on various issues, but American presidential hopeful Rick Santorum – who is a devout Catholic – does not think the pontiff should be discussing scientific topics.

In a recent radio interview in Philadelphia, Santorum said Pope Francis should not be meddling with the scientific world. Santorum is one of the candidates seeking the Republican Party's nomination for the November 2016 US presidential election.

Santorum said the Roman Catholic Church is not exactly a "credible" authority when discussing scientific issues.

"The church has gotten it wrong a few times on science, and I think that we probably are better off leaving science to the scientists and focusing on what we're really good at, which is theology and morality," Santorum told host Dom Giordano on Monday.

"When we get involved with political and controversial scientific theories, I think the church is not as forceful and credible," the lawmaker added.

Santorum made these statements as Pope Francis is preparing a highly anticipated encyclical calling for global action on climate change, which he had earlier described as a moral and religious imperative.

The Pope, who earned a master's degree in chemistry before becoming a priest, is expected to release the encyclical in the coming weeks. He earlier attributed changes in climate patterns to human activities.

Differing sharply with the Pope, most world leaders and environmentalists, Santorum has called climate change "a hoax," saying changes in weather patterns are just natural. Most Republicans also believe that global response to climate change will have a negative impact on the US economy.

This was not the first time Santorum expressed an opposing view with Pope Francis. The lawmaker also does not subscribe to the idea of evolution, while Pope Francis says evolution does not contradict with Church doctrine.

The Republican presidential hopeful nevertheless described himself as a "huge fan" of Pope Francis, particularly of his stand on family issues.