The presenter was fined £86,000 ($123,200) and banned from driving for 20 months, the BBC reported.
The reporter put the incident down to the media crowd gathering outside of the court, and the busy atmosphere.
Ant admitted he was more than twice the legal limit after his Mini collided with two other cars in west London last month.
Speaking outside of the court, the Saturday Night Takeaway host said: "I let myself down, I let a lot of people down".
McPartlin was breathalysed at the scene and found to have 75 microgrammes of alcohol in 100 millilitres of breath.
As Ant faced his verdict at Wimbledon Magistrates Court on Monday, it emerged that he was twice the legal limit when he crashed with his mum Christine Woodhall in the auto.
The driver of one of the cars said in a witness statement that he and his wife "could have died as a result of Mr McPartlin's reckless driving".
"I just want to say that I'm truly sorry", he said outside court.
Liam Walker, Ant's defence barrister said: "Anthony McPartlin is sorry".
"Through me, Mr McPartlin wishes to express both sorrow and regret over his actions", Mr Walker said.
'He knows it is right that he's here and he hopes that which has led him here will eventually help him'.
Walker earlier said: 'But for good fortune the consequences could have been worse. And for that I am truly sorry.
Freeman jumped after the crash, before apologising to viewers and saying that "some cars have just crashed". "He feels the guilt that is reflected in his plea".
The 42-year-old was twice over the legal alcohol limit when he was involved in a three-car crash in London on March 18.
The presenter faced a scrum of photographers and reporters as he walked up the steps to Wimbledon Magistrates' Court this afternoon to answer to the charge against him.
The BBC reports that in a letter read out in court, the TV presenter stated that the events were a "turning point" for him and that he had let himself "and so many others down".