Lewis Edwards posed as a teenage boy to target more than 200 girls between 2019 and February this year and manipulate them into sending him indecent images.

Lewis Edwards, 24, admitted 162 offences of child sexual abuse against girls aged 10 to 16, whom he also blackmailed with the threat of exposure, Britain's Crown Prosecution Service (CPS) said.

Edwards posed as a teenage boy to target more than 200 girls between 2019 and February this year and manipulate them into sending him indecent images.

Some victims begged him to stop, but he demanded further images, using threats and blackmail, prosecutors said.

Edwards received some of the images while on duty as an officer in South Wales. Detectives found he possessed heavily encrypted electronic devices alongside a blackmail manual.

"The public will be as shocked and sickened as we are that such appalling offences were committed by a serving police officer," said Danny Richards, assistant chief constable of South Wales Police. Edwards was given a life sentence at Cardiff Crown Court and will spend a minimum of 12 years in jail.

"He has caused significant harm to the victims, to their parents, their siblings and their wider families," Judge Tracey Lloyd-Clarke said.

"It is clear that he not only gained sexual gratification from his offending but that he also enjoyed the power and control that he had over these young girls. His reaction to their distress can properly be described as cruel and sadistic."

Trust in Britain's police forces has been badly damaged in recent years following a series of major scandals, including officers being convicted of murder and rape.

London's Metropolitan Police, Britain's largest force, this year began reviewing its handling of previously closed complaints against nearly 1,100 officers and staff over the last decade, including allegations of sexual assault.

"Any sexual exploitation of young people is abhorrent and our hearts go out to the victims in this case," said a spokesperson for Snapchat.

They said the app used technology to detect and prevent such abuse and provided extra protections for under-18s, including a recently-added warning about being contacted by strangers and a feature for parents to monitor activity.