It was reported that the couple had left a charity auction at Home House, an exclusive private members' club in central London, but began arguing as they shared a taxi back to their Marylebone home.
The Sun reports that the couple begun arguing after Mrs Goldsmith confronted her husband about his cocaine use.
He was screaming and swearing at her and she slapped him round the face and his glasses fell off. It kicked off as they tried to unlock door,' a source told the publication
'He then turned and hit her in the face with a left hook. She fell and cracked her head on the pavement.'
'They seemed to have had a good drink and she was upset with him and saying, 'I haven't seen my husband for a week and you go and leave me to do cocaine with your business buddies',' the source added.
‘She said, 'Do you think I'm stupid'? He started yelling at her and saying, 'You're a dirty whore'.
‘He was being rude to me as well and boasting of spending £100 a day on cabs. I pulled up at their home, she got out and he paid the fare.
'He then got out and started taking over from her to unlock the front door. That's when it kicked off.
'She slapped him before he appeared to punch her. I jumped out of the cab and said, 'You can't do that'. I started ringing 999 and he began taking pictures of my cab — saying, 'I'm going to report you'.'
Mr Goldsmith is the brother of Kate’s mother, Carole and has previously earned the reputation of 'black sheep' of the family.
The incident occurred at around 1.30am on Friday morning, the Times reported – Mr Goldsmith was held in custody yesterday for questioning, but was charged last night and has now been bailed to appear in front of magistrates, later this month.