Christian campaign group CARE is calling for urgent action after figures obtained by the BBC revealed a dramatic increase in reports of children sexually abusing other children.
Cases doubled in the two years to 2019, with between 15,000 and 16,000 reports in 2018 and 2019.
This far surpasses the figures for 2017, which stood at nearly 8,000.
Reports included rape and assault but the figures did not include non-consensual sharing of private sexual images or videos.
Dr Rebekah Eglinton, chief psychologist for the Independent Inquiry into Child Sexual Abuse, told the BBC's Panorama programme that internet pornography is directly motivating attacks.
"What children have said to us is that sexual violence is now completely normalised through social media platforms [and] through access to online pornography," she said.
She added that unwanted touching and pressure to share nude photos have become so commonplace that many children "wouldn't bother reporting it".
CARE has called the increase in sexual abuse among children "alarming" and said it was the "price of government inaction" on pornography.
The group said children have been "badly let down" by the government's failure to implement pornography safeguards, especially age verification.
CARE spokesman James Mildred is calling on ministers of all parties to work together to force the government to act on online safety.
"These deeply disturbing figures must serve as a wakeup call to UK ministers whose policy decisions have badly let down children," he said.
CARE has long been campaigning for tighter restrictions on access to internet pornography.
In 2017, Part 3 the Digital Economy Act was passed which would have introduced age verification, effectively blocking access to porn sites for under-18s, but the plans were abandoned in 2019.
Mr Mildred continued, "The government had the chance to implement age verification safeguards, limiting access to pornography sites by children in 2017.
"Instead, it dithered and delayed before scrapping the plans in 2019. That decision led to children continuing to access degrading and violent pornography, which motivated attacks in the offline world."
Research by Savanta for CARE in June found that eight in 10 UK adults support the introduction of age verification controls for online pornography.
Mr Mildred added, "The public strongly supports a move towards stricter regulation of porn sites. Ministers have no excuse for continuing to ignore them and particularly parents who are deeply worried about what their children are accessing online.
"We call on ministers to do the right thing and usher in age verification immediately.
"Children shouldn't have to wait years until the government's online safety regime is ready to be enforced. They need protection now."
The government is facing a legal challenge over its failure to implement Part 3 of the Digital Economy Act by father-of-four Ioannis Dekas and student campaigner Ava Vakil.
Representing them in the case is Paul Conrathe, solicitor with Sinclairslaw, who said: "Despite it being the clear will of parliament that age verification should be put in place as soon as possible back in 2017, the government have failed to act.
"It is astonishing that faced with clear evidence that online violent pornography is widely accessed by children and harmful to them the government dithers and prevaricates.
"The findings of this poll vividly show the depth of concern felt by people at the harm that is being experienced by children and the need for age verification."