More than a quarter of a million reports of online images and videos of child sexual abuse were dealt with by the Internet Watch Foundation in 2019.
Of this record number of reports, more than 132,000 contained child sexual abuse material, up 26% on 2018 and double the number identified in 2016.
The charity said much of the abusive content is available on the open internet, as opposed to the dark web.
Chief executive Susie Hargreaves described it as an "epidemic".
"What's really shocking is that it's all available on the open internet, or 'clear web'," she said.
"That's the everyday internet that we all use to do our shopping, search for information, and obtain our news."
Ms Hargreaves said it was "really shocking" to find the number of reports going up.
The charity's hotline manager, who asked to be identified only as Chris, said there were several factors behind the increase, including better staff awareness and expertise.
"We look at every report which comes into our hotline, but not every report leads to child sexual abuse content.
"Whilst we actively encourage people to report to us content within our remit because it helps us do a good job, actually, far too many people are wasting our time," Chris said.
"Our analysts have to look at everything they're sent. So, our message is, yes please report to us, but please, please stop reporting material outside our remit."
'Dose of reality'
The IWF works to find and remove online sexual abuse content, and false reports to the charity in 2018 cost £150,500 - the equivalent of 4.3 years' worth of analyst time.
Its website provides a list of organisations to help members of the public to report material to the correct place.
The charity, which launched in 1996, began actively carrying out its own searches as well as reacting to reports in 2015.
Ms Hargreaves said: "Child sexual abuse is an horrific topic for people to talk about, but as a society we have got to take on board a heavy dose of reality and face up to what's right in front of us."
If you have been affected by the issues raised in this article, help and support can be found at BBC Action Line.