A FATHER-to-be who enticed a 'vulnerable' girl in care to perform sex acts in a park has been thrown behind bars for two years.

Mark Shirley left his victim feeling 'angry and used' when he deserted her in the green space after having sex to go to an ultrasound scan of his unborn baby.

The 21-year-old confessed he had been chatting to his 15-year-old victim on Facebook messenger despite being forbidden from contacting her.

The teenager, who lived in an Oxfordshire care home and cannot be named for legal reasons, feared she had fallen pregnant after the incident.

Sentencing at Oxford Crown Court on Tuesday, Judge Maria Lamb slammed the defendant for 'knowing perfectly well' his victim was underage.

She said she took with a 'pinch of salt' Shirley's protestations he was in love with the teenager despite being in a sexual relationship with the mother of his unborn baby.

Judge Lamb locked him up for two years and also slapped him with a 10-year sexual harm prevention order banning him from having any contact with girls under 16 and going on social media.

The youngster first revealed to care home staff she had sex with Shirley, who was known to them, in August last year, prosecutor Jane Davies said.

But the police investigation was 'discontinued' after the teenager told officers she was unwilling to support a prosecution against the defendant.

Shirley, who had been arrested and interviewed, was released on bail and told not to contact the youngster, the prosecutor said.

The sex offender, of Elms Drive, Marston, was arrested again three months later after care home staff discovered the pair had been chatting and had sex.

The teenager later revealed to officers she contacted Shirley online after arguing with her ex-partner on Halloween, asking to meet him the next day.

But he replied 'why not now?', and the pair met in the early hours of the morning, when Shirley kissed her and had sex with her.

He then told the teenager he had to leave as he had a ultrasound scan to get to later on in the morning and blocked her from contacting him.

Defence barrister Gordana Turudija-Austin denied Shirley, who had no previous convictions, had 'groomed' his victim, claiming he initially believed she was 17.

She added: "There was simply no targetting of [the victim] just because she was vulnerable. They met by chance, they met in a field, where they had a conversation."

Shirley, who suffers from dyslexia and aphasia, was addicted to drugs at the time but 'simply stopped' using when he was remanded into custody, the barrister claimed.

The defendant, who must sign the sex offenders register for 10 years and pay a victim surcharge, did not contact the teenager 'for a period of time' after officers disclosed she was underage.

Shirley, who appeared via video link from HMP Bullingdon, admitted causing or inciting a child to engage in sexual activity on October 31 last year and sexual activity with a child on November 1 last year.