The latest incident will deepen concerns that the force – which for decades has regarded itself as “Asia’s finest” – is facing an integrity crisis, the recent case bringing the total number of arrests this year involving officers to 30.

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According to sources, on the night of July 21, the officer went for a drink in Lan Kwai Fong with three women, including the 14-year-old. He had met all of them online.

The group “drank heavily”, according to one source, and the detective constable accompanied the girl to her home on a Sha Tin public housing estate. The officer was suspected to have raped the girl in the staircase outside her family home.

When the girl arrived home her mother noticed signs from her dishevelled clothing that she might have been assaulted, at which point the girl told her she “had sex with the man”. The mother then called police.

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Detectives from the New Territories North regional crime unit launched an investigation and the officer was arrested at his home in Kowloon East on Thursday. During the raid on his home, sources said officers discovered the clothes the man wore at the time of the incident.

Separate sources said the same officer had been arrested in May this year on suspicion of indecently assaulting two girls he met online. He was on bail from his arrest in May when the alleged Sha Tin attack took place.

Tang said the force was distressed over the increasing number of arrests among its ranks and vowed zero tolerance of any misconduct by officers.

Police had not responded to inquiries about the cases involving the 32-year-old detective constable at press time.