A female police officer who had sex in a McDonald's toilet with a rape victim she was supposed to be looking after has been jailed for 22 months.

PC Charlotte Peters, 33, started the affair in February this year with the vulnerable woman who had been raped by a stranger and had been assigned to her as a liaison officer.

The PC, with the Met's Sexual Offences, Exploitation and Child Abuse Command, first kissed the woman while taking her fingerprints, and they met for sex four times in less than a month.

The affair was exposed on March 14 when the rape victim, believing Peters would not leave her girlfriend, told staff at the home where she was staying she was "tired of being her dirty little secret".

Peters then demanded the woman delete texts they had exchanged when she realised news of the relationship would reach her police bosses, threatening to kill herself.

Southwark crown court heard, in the fallout, her lover was hospitalised after slashing her wrists.

Peters pleaded guilty to misconduct in public office last month, and was on Wednesday jailed for 22 months.

Judge Anthony Leonard QC said the fallout after the relationship was revealed "truly underlined how inappropriate it was to start a relationship with someone so vulnerable.

"It beggars belief someone who seems to be so admired by other officers allowed yourself to do so," he said.

He said that Peters was "there to support her, not to cause her further distress and difficulties", adding: "You must have realised as soon as it started how inappropriate your relationship was and yet you did nothing to bring it to an end."

Peters sat with her head bowed in the dock while the case against her was outlined to the court, mouthing "love you" to the public gallery as she was led to the cells.

Prosecutor Kate Bex said Peters, a Sexual Offences Investigative Techniques officer, would "be expected to recognise vulnerability" in her job and was in a position of trust".

"The first sexual contact was a kiss, and followed a couple of days later by consensual intercourse at the victim's grandfather's home address when Ms Peters arranged to meet her to sign a fingerprint form", she said.

"Ms Peters was at work when she attended to see the victim in order to have her sign the form, they had sexual intercourse, she went back to work and met the victim later in Whitechapel when off duty."

Peters and the woman had sex at the grandfather's house again on March 1, and they met for a tryst at a hotel in Barking a week later.

"The final meeting took place at Liverpool Street Station, where it is suggested there was sexual intercourse in the lavatories at McDonalds", said Ms Bex.

She added: "The woman told a member of staff that she had broken up with Peters because she realised Peters was never going to leave her girlfriend. She was tired of being her dirty little secret."

She later claimed to have made up the affair for attention, but police were called by staff.

"The victim described how Ms Peters reacted to the disclosure to staff. She threatened to kill herself which itself would inevitably have placed considerable pressure on the victim", added Ms Bex.

"The disclosure and the fallout culminated in the victim then cutting her wrists and admission to hospital."

Peters stayed silent in her first interview, but when quizzed again she issued a prepared statement admitting the affair.

Kevin Baumber, defending, said the officer will not challenge misconduct proceedings against her and she will now lose her job.

He said the effect on Peters' personal and professional life are "tragic", but she knows she has "gone gravely wrong".

Mr Baumber urged the judge to suspend the prison sentence imposed on Peters so that she could start rebuilding her life, saying she is an "exceptionally caring person".

Peters, of Hatton Place, Luton, Bedfordshire, pleaded guilty to one count of misconduct in a public office.