A US Secret Service agent tasked with protecting the White House has started a 20-year stretch for sending explicit snaps to underage girls – sometimes while on duty.

Lee Robert Moore, 38, a uniformed member of the Secret Service, pled guilty in March to charges of enticement of a minor to engage in sexual activity and attempting to transfer obscene materials to a minor. He was caught in a sting operation run by the Delaware Child Predator Task Force.

Police officers created an account on the Meet24 and Kik mobile apps for a fictitious 14-year-old girl who Moore chatted up over two months. He sent numerous messages using the screen name RobertTheW1se and at least one obscene image taken while on duty. He sent it to the cops' undercover account, asking the girl to send her own images.

Moore was arrested at his Maryland home on November 9, 2015, and initially denied any wrongdoing. He later 'fessed up to messaging the fake account, and engaging in similar messages with 14-year-olds in Florida and Texas, and with a 17-year-old in Missouri.

He was fired from the Secret Service, and has been held in custody ever since. Moore was sentenced to 20 years in a federal prison by US District Judge Daniel Hurley on Thursday. ®