PC Hannah Notley from Benfleet in Essex, cried in the dock at Inner London Crown Court last month as she pleaded guilty to a charge of misconduct in a public office.
The 30 year old failed to correct the assumption of her superiors at Essex Police that the case had been investigated and passed on to the Crown Prosecution Service.
She then told the complainant, whose alleged attacker is currently awaiting trial, that it had been decided that no further action would be taken.
She will be sentenced at Southwark Crown Court today.
More top news
Turning cloudy and windy but feeling mild at the weekend.
The Ukip leader also says his children his hid in a graveyard and were brought back by police.
Here's a borough-by-borough breakdown of the official figures.