A 17-year-old girl was sexually assaulted three times by three separate men within an hour in an “unprecedented” and gravely traumatising ordeal.

The teenager was walking home from a nightclub in Tower Hamlets, east London, when she was targeted by the men in quick succession.

The local authority announced on Friday that it was investing £3million to put an additional 19 officers on the streets in the crime-ridden borough after losing almost 200 officers in seven years due to government cuts.

Police said there was absolutely no link between the “opportunistic” attacks on the teenager, two of which were described as very serious, possibly rape. The third suspect may have been part of a group.

The victim, who is a student, was so deeply traumatised that her memory was affected. Officers fear she may have been drugged.

It is hoped that the men will be identified by CCTV images, one of whom in particular - the second suspected attacker - is clearly pictured.

The girl’s ordeal began shortly before midnight on Friday September 29. She had spent the evening at a club with friends but became separated from them and was trying to make her way home.