After he was formally charged, police later revealed Ant was twice over the legal limit when he was arrested.
He was originally scheduled to appear in court on 4 April, however, his hearing was adjourned.
Prosecutor Katie Sinnett-Jones told Wimbledon Magistrates' Court on Monday that the incident happened at around 3.50pm when McPartlin drove his Mini around a "sharp bend and lost control" then ended up on the wrong side of the road.
Ant was found to be twice the legal limit when he crashed his auto into two other vehicles in South London on March 21.
In a statement read by Ms Sinnett-Jones, he said: "Myself and my family were in deep shock as we believed we could have died as as a result of Mr McPartlin's reckless driving".
District Judge Barbara Barnes ordered him to pay an £86,000 fine, and suspended him to a 20-month driving ban, which could be shortened to 15 months on completion of an awareness course.
The court heard that the driver of the other Mini said afterwards he thought he and his family were going to die in the collision.
McPartlin pleaded guilty to the charge, with officials confirming that his breathalsyer test had a reading of 75 mcg of alcohol per 100ml of breath - more than twice the legal limit of 35 mcg.
In an unbelievable turn of events, there was a auto crash right outside the court where Ant McPartlin's drink drive case was going on today.
"I'm truly sorry for what happened", Ant said in a brief statement after leaving court just moments ago. For that I'm truly sorry. "Higher standards are expected of me".
He added that he was thankful "no-one had been hurt" in the three-car crash, which occurred in Richmond, London, on 18th March.
'I accept full culpability for this and wish to apologise to all those concerned'.
McPartlin and Donnelly are among the best-known presenters on British TV, fronting primetime entertainment formats for ITV such as "Saturday Night Takeaway", "Britain's Got Talent" and "I'm a Celebrity, Get Me Out of Here!"