The children’s charity called for more to be done to tackle abuse in private messaging.
The social media giant has previously revealed plans to make messaging across its apps, including Instagram and Facebook Messenger, end-to-end encrypted.
However, the NSPCC argued that these figures, which were gathered through Freedom of Information requests to police forces, show that Facebook's encryption plans will leave children at greater risk.
The charity also accused the social media giant of "turning back the clock on children's safety".
What the data showed
The NSPCC said the data it received showed 9,477 instances of sexual or indecent image offences against children were recorded by police between October 2019 and September 2020 where the communication platform was known, with 52% taking place on Facebook-owned apps.
The figures showed that Instagram was used more than any other Facebook platform - in more than a third of all instances, ahead of Facebook Messenger and WhatsApp.
The data were gathered from 35 police forces in England, Wales and the Channel Islands.
What the NSPCC has said
The NSPCC argued that should Facebook go ahead with its encryption plans, many of these offences could go unreported in future unless new safeguards were put in place.
As a result, the charity has urged the Government to strengthen the powers of the forthcoming Online Safety Bill to allow the proposed regulator, Ofcom, to take action against firms whose design choices could put children at risk.
It argues that although end-to-end encryption offers a number of benefits, including improved privacy, it will hinder the ability of platforms and law enforcement agencies to identify and disrupt child abuse.
"Facebook is willingly turning back the clock on children's safety by pushing ahead with end-to-end encryption despite repeated warnings that their apps will facilitate more serious abuse more often," said Andy Burrows, NSPCC head of child safety online policy.
"This underlines exactly why (Culture Secretary) Oliver Dowden must introduce a truly landmark Online Safety Bill that makes sure child protection is no longer a choice for tech firms and resets industry standards in favour of children.
"If legislation is going to deliver meaningful change it needs to be strengthened to decisively tackle abuse in private messaging, one of the biggest threats to children online."
Last month, a senior official at the National Crime Agency said Facebook's encryption plan "poses an existential threat to child protection".
End-to-end encryption is the practice of securing communications from everyone but the participants, including the platforms hosting the conversation.
What Facebook has said
In response to the research, a Facebook company spokesperson said: "Child exploitation has no place on our platforms and we will continue to lead the industry in developing new ways to prevent, detect and respond to abuse.
"For example, last week we announced new safety features on Instagram including preventing adults from messaging under 18s who don't follow them.
"End-to-end encryption is already the leading security technology used by many services to keep people, including children, safe from having their private information hacked and stolen.
"Its full rollout on our messaging services is a long-term project and we are building strong safety measures into our plans."