Paedophiles used Facebook apps to groom child sex victims more than 40 times in Suffolk last year, and it is feared that figure could rise dramatically as encryption rules change.

Under new measures to make the social networking site more secure Facebook, and the associated Messenger app, will no longer be able to scan private messages and flag content to authorities.

The NSPCC submitted Freedom of Information requests to police forces across the UK and found that in Suffolk Facebook apps were reported to be used 41 times in connection with cases of child abuse images and child sex offences last year.

Across the East of England, the apps were used in 500 cases.

They fear that the plans for encryption could lead to thousands of cases of child sex crimes going unreported.

Andy Burrows, NSPCC head of child safety online policy, said: "For far too long Facebook's mantra has been to move fast and break things but these figures provide a clear snapshot of the thousands of child sex crimes that could go undetected if they push ahead with their plans unchecked."

Detective Superintendent Jeff Yaxley, head of joint cyber and serious crime for Suffolk police, said: "We note the views of the NSPCC with interest - their figures are unfortunately a true reflection of the crime types that we investigate.

"Social media platforms can be a potential 'playground for predators' so making sure that young people and their parents/carers/guardians are aware of these dangers is very important in reducing the risks of grooming online."

He added: "I would appeal to all parents to monitor their children's online activities and check what apps or messaging platforms they are using - the best way to stay informed is for parents/guardians/carers to be totally involved - and talk to openly about online safety and make them aware of the dangers around them."

A spokesman for Facebook said: "There is no place for grooming or child exploitation on our platforms.

"We work closely with child protection authorities in the UK, and we're consulting with experts on the best ways to implement safety measures before fully implementing end-to-end encryption."

The spokesman said they currently use technology to pro actively remove material and are "developing further ways to detect patterns of harmful behaviour in order to ban and report those responsible".

Further advice from Suffolk police can be found here.