According to a statement by Aargau cantonal police, Müller, 63, was driving his Mercedes coupé towards Lenzbourg in the canton of Aargau on September 10th when, for unknown reasons, his car drifted into the left carriageway and hit a scooter coming in the opposite direction.
Witnesses called emergency services and administered first aid to the 17-year-old driver of the scooter, who suffered fractures to both legs.
In a statement posted on the FDP website on Saturday, Müller said he was suspending his election campaign for a seat in the Council of States, the federal assembly's upper house, “out of respect for the young woman and her family”.
“I will continue my work as national councillor and as president of the liberal-radicals,” he added.
Müller also used his statement to defend his behaviour following the accident, which was criticized by some media outlets including Blick.
Speaking to the daily paper, the father of the victim said Müller did not stop immediately after the accident, but 300 metres down the road.
When he did return to the scene, he didn't try to speak with the girl's father, who was by then present at the scene.
In his statement, Müller said “After the accident I was in a state of shock and therefore I stopped my vehicle only at the next possible parking spot and immediately returned to the site of the accident.
“I didn't know that the father of the young woman was there. I didn't know him and the police didn't tell me that one of the young woman's parents was there.
“Naturally I would have sought to speak with him.”
Müller added that he was only told the identity of the victim on Friday morning, after which time he immediately contacted the family.
Prosecutors have opened an investigation into the crash to determine why Müller's car drifted over the centre line.
Police confirmed that the politician was not under the influence of alcohol at the time of the crash.
As is normal in such cases, Müller's driving licence has been temporarily suspended.
According to Blick the 63-year-old is a “gifted motorist” who was an amateur racer before turning to politics.
The centre-right FDP has refused to comment on the incident, reports newspaper Le Temps, considering the accident a personal matter.
The federal elections will take place on October 18th.