Mr Ratner was banned from driving for 21 days and fined pounds 160 for speeding after the court at Thame, Oxon, assessed his disposable weekly income.
Before his sacking as chief executive of the troubled jewellery group last November, Mr Ratner earned pounds 375,000 a year. At that time he was also given a pounds 375,000 pay-off for loss of office.
Under a new system that came into force in October, fines on motorists are based on their disposable income.
The magistrates heard how Mr Ratner was clocked doing between 110 and 114mph on the M40 motorway at Waterperry, Oxon, on 12 October last year.
Asked what he had to say in his defence, Mr Ratner, who represented himself, said: 'There is not very much to say about it, other than that I apologise to the court . . . Unfortunately on this occasion I was not concentrating on the speedometer.'
Asked by the presiding magistrate how a ban would affect him, Mr Ratner replied: 'It would have a large effect. I am looking to acquire a shop and start up in business again.'
Speaking later outside his pounds 400,000 home in Bray, Berks, Mr Ratner said of the pounds 20 a week calculation: 'If you find out how they came to that figure, I would love to know.
'There is some sort of means form that asks you basically if you are unemployed. I just filled that in, that's all.'
Asked if he really was down to pounds 20 a week disposable income, Mr Ratner would not answer. But when a reporter said: 'I hope you have got more than that,' he replied: 'Absolutely.'
The offence took place less than two weeks after Mr Ratner faced hostile demands for his resignation at a shareholders' meeting.
His notorious remark two years ago that a Ratners product was 'crap' is regarded as exacerbating the group's problems.Reuse content