More than 20 people were seriously injured at the Paqpaqli event in Malta in October when Paul Bailey, from Rutland, lost control of the supercar.
A magisterial inquiry found he was driving at "excessive speed" and was not a professional driver.
But the report also said there were inadequate safety measures in place.
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Mr Bailey, who owns several supercars, was taking part in the annual Paqpaqli event in aid of charity when he lost control of the Porsche 918 Spyder, spinning on the airport runway and crashing into spectators.
More than 20 people were seriously injured - including a six-year-old girl - and one remains in hospital, the Times of Malta reports.
There were no mechanical faults with the car, the report concluded.
A spokeswoman for the Maltese Ministry for Justice said: "The driver lost control of the vehicle because he was driving at an excessive speed.
"In addition, although the driver is a supercar enthusiast, and owns a large collection of supercars, the inquiry concludes that he is not a professional driver and that he lacked the necessary skills and ability to drive the supercar in question at such high speeds.
"In fact, his lack of experience in terms of handling techniques and corrective measures was a factor which contributed to the loss of control of his vehicle."
But the inquiry also concluded that health and safety measures were not taken including a lack of signage on the circuit, no concrete safety barriers and a poorly designed chicane.
It was reported Mr Bailey was the first person in the world to own a Porsche 918 Spyder, a McLaren P1 and a Ferrari LaFerrari - known as the "holy trinity" of hypercars.
A British millionaire was the main cause of a crash which saw dozens of people injured when a Porsche ploughed into spectators, a report concluded.