Pope Francis has said that technology company executives and investors must be held accountable if they put profit before the protection of children from harm, including the damage caused by easy access to pornography on the web.

The pontiff was opening a Vatican conference on "Promoting Digital Child Dignity" that has brought together companies like Apple Inc,  Google's owners Alphabet Inc, Microsoft Corp and Facebook and child protection groups as well as law enforcement and judicial officials.

"Companies that provide (internet) services have long considered themselves mere suppliers of technological platforms, neither legally nor morally responsible for the way they are used," he said.

"There is a need to ensure that investors and managers remain accountable, so that the good of minors and society is not sacrificed to profit."

The pope said the Catholic Church's "painful and tragic experience" with its own sexual abuse crisis gave it a "duty to approach these issues with a long-term vision".

Last month, the United States, Britain and Australia called on Facebook to suspend plans to encrypt its messaging service, saying it would hinder the fight against child abuse and terrorism.

Child predators have increasingly used messaging applications to groom their victims and exchange explicit images and videos. The number of known child sexual abuse images has soared from thousands to tens of millions in just a few years.

Facebook chief executive Mark Zuckerberg has said he was "optimistic" his company would be able to identify predators with the same tools it uses to combat election interference.

One prominent attendee at the conference is Queen Silvia of Sweden, a long-time activist for children's rights.

Citing studies that show the average age of first access to digital pornography is 11, the pope said companies must make greater efforts to identify the age of users and intensify cooperation with law enforcement to combat child pornography.

"I make an urgent appeal to them to assume their responsibility towards minors, their integrity and their future," he said.

"It will not be possible to guarantee the safety of minors in the digital world without the full involvement of companies in this sector and without a full awareness of the moral and social repercussions of their management and functioning."

This year, Britain's National Association for the Prevention of Cruelty to Children proposed that technology company directors be made legally responsible for child safety.

The conference at the Pontifical Academy of Sciences is the Vatican's latest foray into moral issues related to technology.

In September, another Vatican department brought together Silicon Valley heavyweights, Nobel laureates and cyber experts to discuss the ethical use of artificial intelligence (AI).

This morning, Pope Francis urged computer engineers to strengthen ways of using AI and algorithms to protect children on the internet. He said they should feel "personally responsible for building the future".