The Internet Watch Foundation made the call ahead of a conference led by the Pope in Vatican City on Thursday to focus on fighting the problem.
Susie Hargreaves, chief executive of the Cambridge-based charity which works to remove images and videos of child abuse from the internet, said religious leaders need to do "a lot more" to face up to "what has happened in the past".
The National Crime Agency estimates 144,000 users from the UK are active on the dark web, looking for images of sexual abuse.
Less than 1 per cent of content is hosted in the UK, but the demand is "significant", the charity said.
Speaking ahead of the two-day event where the charity will present its research, Ms Hargreaves said: "It is something to be applauded that all the different religious leaders are getting together to talk about the problem and stepping up, although there is a lot more that can be done, and a lot more public acknowledgement as well of what has happened in the past."
Religious leaders have a "great deal of influence" and their help in combating child abuse online would be "invaluable", Ms Hargreaves said, adding: "The Catholic Church and other religions have huge influence, they are meant to be taking a moral lead."
After an address by the Pope, the conference will hear from Sheikh Saif Bin Zayed al Nahyan, the deputy prime minister of the United Arab Emirates, Queen Silvia of Sweden, and Bartholomew I, the Archbishop of Constantinople, representing the Eastern Orthodox Church.
They will be joined by experts from around the world, including representatives of international organisations, NGOs, technology companies, politicians and religious leaders.
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