Ashton, an emergency doctor at St Richard's Hospital in Chichester, West Sussex, now faces being struck off at a Medical Practitioners Tribunal Service hearing in Manchester.
He allegedly told the woman, a nurse at the same hospital that she 'turned him on' and asked her to touch herself after obtaining her number from her medical records.
The woman, known as Patient A said she was 'confused' by the call and knew he was performing a sex act because of the noise he was making, during a Medical Tribunal hearing in Manchester. It was also alleged that he touched her bottom in a separate incident.
Talking about the phone call, Counsel for General Medical Council, Carlo Breen, said: 'Dr Ashton asked Patient A what underwear she was wearing and said he wanted to touch her.
'He told her he wanted to be inside her. At this point, Patient A realised the doctor was masturbating because of the tone of his voice and the noises he was making.
Describing another alleged encounter when Ashton visited Patient A's flat, Mr Breen said: 'He started asking about her sex life and if she still had a boyfriend.
'They were sitting on the sofa and she says he put his arm around her and put his hand up her jumper and touched her breast.
'He said he wanted to touch her "down there". Patient A said she didn't want him to do that. She didn't like him touching there but at the same time she was scared in case he got angry. The circumstances concerning the conduct of Dr Ashton are wholly inappropriate.'
Dr Ashton is also accused of being inappropriate with another woman who had been admitted to A&E in May 2009 after injuring her ankle while on a fancy dress night out.
During the consultation, he is said to have told the woman - Patient B - that he liked her outfit and her friend's cowgirl costume, then asked her to walk up and down the ward to show off her hotpants.
Four days later, he phoned the woman and said she may have broken a bone, but rather than telling her to revisit the hospital he arranged to go to her house 45 minutes away, it is claimed.
Arriving in sandals and shorts, he again told her he liked her outfit, asked if she had a boyfriend and asked if she liked dressing up, it is alleged.
When he left the address an hour after arriving, he sent a Facebook friend request to Patient B and messaged her friend saying he 'loved her cowgirl hat', it is said.
Dr Ashton, of Chichester, denies all of the allegations of sexually motivated conduct - and claims Patient A was 'fixated' with him.
The hearing continues.