The US is running out of exorcists.

During the last 10 years the number of Roman Catholic priests officially designated as exorcists has quadrupled from 12 to 50.

However, in an interview with the Daily Telegraph, two of them – Fr Gary Thomas and Fr Vincent Lampert – say they are struggling to keep up with demand for their services.

The Catholic Church downplayed the reality of Satan and demonic forces after the liberalising Second Vatican Council in the 1960s. However, the conservative Pope John Paul II was clear about his belief in the occult and Pope Francis has also reminded Catholics that "Satan is real".

The increased demand for rites of exorcism may also be related to an increase in the number of US films and TV shows dealing with the subject.

Fr Lampert told the Telegraph: "We're gaining all sorts of knowledge, but there's still that emptiness within us that is being filled with addictive behaviour such as drugs and p***ography.

"There's a line in the Old Testament that says when one grows in knowledge one also grows in despair. The decline in faith goes hand in hand with the rise in evil."

He also said an exorcist was "trained to be a sceptic".

"The first line of defence is not to see the Devil everywhere but to determine what this person is up against," he explained. "The overriding goal is to bring relief into the life of the person who's suffering, whether that suffering be due to psychic or spiritual problems."

Fr Thomas said of those who came to him: "Often the stories are very complicated and many have been suffering for a long time." He said they were "desperate" people who had had no help from psychology and psychiatry.

"They're sick in one way or another," he said. "And sometimes they do have a demonic problem."

He said: "I am a full-time pastor and this is a very intense ministry. Almost every free night that I have is taken up with exorcisms.

"I could conduct one or two exorcisms a week for demonic attachment (as opposed to full possession). People could be quite functional but once they get into a sacred arena, such as a church, or participate in some element of parish, they'll begin to manifest or they'll begin to get sick or they'll begin to show other kinds of signs that something is amiss. And it's my role and my team's to discern what it is. Is it something psychological?"

Fr Thomas has a "discernment team" composed of medical doctors, clinical psychologists and psychiatrists. He said some people seeking help may not be demonically possessed but may have some kind of demonic oppression in which they are depressed or feel malaise.