McPartlin, 42, was involved in a collision with two other cars while he was driving his Mini in Richmond, west London, and was arrested at around 4pm on Sunday after failing a roadside breathalyser test.
A source told the website: 'He's just really upset about it all just on so many levels - gutted and anxious about Ant obviously and devastated he's going back to rehab.
"Officers, London Ambulance Service and London Fire Brigade attended".
Police previously confirmed that a number of individuals were treated at the scene for minor injuries, and a child passenger from one of the cars was taken to hospital to be checked as a precaution.
Road safety charity Brake said four people are killed by drink-driving on United Kingdom roads every week.
It's since been confirmed that Ant will step down from current TV commitments and return to treatment.
This latest disaster comes hot on the heels of Ant's recent spell in rehab after admitting to an addiction to painkilling drugs and alcohol.
It comes after a statement from Ant & Dec's publicist said: "Ant has made a decision to go back into treatment and step down from his current TV commitments".
The show is not airing this weekend, with the final two episodes, now scheduled for 31 March and 7 April, not featuring McPartlin.
"Suzuki will remain in dialogue with ITV and advise media when appropriate regarding the last two episodes of the series".
Holly and Phillip say they are "shocked and saddened" by Ant McPartlin drink driving incident on "This Morning".
"Some people might not understand it but our friendship is a massive, massive part of where we are today". "We can't say much more because the matter is still being investigated by the police", Holly added. "We wish Ant and all those involved in these sad events all the very best".
This has marked the latest in a string of personal setbacks for the star, who first entered rehab a year ago due to his addiction to painkillers.
Lisa Armstrong, Ant's wife who he's now split from and in the process of divorcing, has commented on the arrest and subsequent developments by simply saying: 'I'm sorry, I'm not interested, ' when asked for her thoughts on the matter, according to the Mirror. The pair seemed to be in fine form though, with another win for Best Presenters under their belts at the National Television Awards for the 17th year running.