A former British child abuse detective pleaded guilty Monday to having sex with a 15-year-old girl whose family he had befriended during an investigation.

Andrew Rowe, 31, hung his head after admitting to five sexual offenses — including sex with a child — at Birmingham Crown Court via video-link from a prison across town.

The Staffordshire Police department in central England, where Rowe worked for 12 years, said he had been communicating with the girl through the social networking site Facebook and sent her "hundreds of inappropriate messages" this year. It said he had tried to cover his tracks by deleting electronic evidence of his crimes.

"He ingratiated himself with a family, then betrayed his young victim and her parents who had placed their trust in him as a police officer and as a supposed friend," Assistant Chief Constable Marcus Beale said in a statement. "It is hard to imagine a more shocking abuse of position by an officer."

It was not clear from the police statement how exactly he met the family or how long he had been corresponding with the girl. The crimes were first reported in April, after which Rowe was suspended and then resigned from the force.

The girl's family said two top-ranking Staffordshire officers personally apologized for Rowe's acts.

"The hardest thing at the beginning was the prospect of reporting a police officer to the police, wondering what level of support, if any, we would receive," the family said in a statement.

"We would now urge anybody who finds themselves in a similar situation to report the matter immediately, as we have received the highest level of help and support possible."

Staffordshire Police could not immediately say when Rowe would be sentenced. The telephone number for the local prosecutors' office was out of order Monday.