The football star, 43, previously pleaded guilty to using the device after being spotted by a member of the public on November 21.
His case was initially considered at Bromley Magistrates’ Court last month, through an administrative process known as a single justice procedure, which is not open to the press or public.
Beckham, who appeared in court wearing a dark grey suit and tie on Thursday, was told by District Judge Catherine Moore that he would be disqualified as she gave him six additional points to the six he already had for previous speeding matters.
Prosecutor Matthew Spratt said Beckham was photographed by a member of public as he drove in “slowly moving” traffic while holding a phone.
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He said: “Instead of looking straight forward, paying attention to the road, he appeared to be looking at his lap.”
He added: “He (the witness) says that the defendant was operating a handheld device at knee level. At that moment a photograph was taken.
“The defendant was holding the mobile phone in the upright position.”
Gerrard Tyrrell, mitigating, said his client was travelling slowly and has “no recollection” of this “particular incident”.
He added: “There is no excuse for what took place but his view is as he cannot remember... he’s going to plead guilty and that’s what he’s done.”
Ms Moore was told how Beckham had six points already on his driving licence for speeding.
The first offence occurred in February 2016, while the latter took place in January 2018.
Beckham accepted he drove a loaned Bentley at 59mph in a 40mph zone in west London in January last year but avoided prosecution after enlisting the services of celebrity lawyer Nick Freeman, who is dubbed Mr Loophole.
Beckham did not face further action because a notice of intended prosecution was not received until one day after the statutory 14-day time limit.
Mr Freeman also assisted Beckham in overturning an eight-month driving ban in 1999.
Ms Moore told Beckham on Thursday that she acknowledged the slow pace of the traffic during the November offence in central London but added that there was “no excuse” under the law.
Beckham was also fined £750, ordered to pay £100 to prosecution costs and a £75 surcharge fee within seven days.