Businessman Paul Bailey was driving the Porsche 918 Spyder when it clipped the grass, spun out of control and ploughed through a barrier at Malta's annual Paqpaqli ghall-Istrina motorshow, according to reports of the incident.
Five of the injured were said to be in a critical condition, among them a six-year-old girl.
The driver was among the 26 people injured taken to hospital.
The car was travelling at high speed along an unused airport taxiway in the Hal Farrug district when the accident occurred, witnesses said.
One eyewitness told the Times of Malta: "The car was speeding down the taxiway when a back wheel went on the grass.
"The car spun out of control, went through the barriers where a large crowd was watching, and into the area of the static car exhibition.
"Many people were hit, there was chaos and screams."
A video of Mr Bailey driving the Porsche at some point ahead of the accident has appeared online:
Mr Bailey, a self-made millionaire from the East Midlands, has a collection of more than 30 supercars, including a £866,000 McLaren P1 and £1.2 million customised Ferrari, according to the Mail Online.
He reportedly bought the limited edition Porsche Spyder for £780,000 in January this year.
He made his £28 million fortune when he sold a phone-conferencing firm in 2012, the Mail Online reported.
The rest of the charity event was cancelled following the accident.
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