According to Heise Online, Der Spiegel has seen a copy of a report compiled by Germany's Federal Transport Ministry, which notes several dangerous characteristics of the system.
For example, if the autopilot system is on and there are no lane markings, it simply follows the car in front of it. If that car pulls over, the Tesla simply follows suit, even if there is a car alongside or near it.
The report also claims that Tesla's rearward facing sensors can only detect objects 40 metres behind the car, which is not sufficient when the vehicle is driving along an unrestricted stretch of the autobahn where cars often do over 200km/h.
One government inspector noted how difficult it was override the Autopilot system when the Tesla wanted to move to the left even though there was an approaching car.
Critically, the Autopilot system doesn't give a clear indication to the driver of when it can no longer handle the current driving situation.
In a statement to Reuters, the German transport ministry stated that testing had yet to be completed. Tesla told the news service, "We have always been clear with our customers that Autopilot is a drivers assistance system that requires the driver to pay attention at all times".
Elon Musk, Tesla's CEO, took to Twitter to defend the Autopilot system.
In one tweet, Musk said: "Not actually based on science. Objective data shows Autopilot is safer than manually driven cars."
"[The report is] utter nonsense. Empirical evidence is what matters, not random speculation," the outspoken CEO stated in response to another tweet.