George Michael fell from his vehicle on to the carriageway of the M1 motorway, an eyewitness has claimed.
The star was airlifted to hospital with a head injury following the accident on Thursday, although his publicist Connie Filipello passed his injuries off as "superficial cuts and bruises".
But another driver who was behind the 49-year-old singer's vehicle has told The Sun she saw him lying on the road surface smeared with blood.
Katherine Fox, 23, said he was wearing a ripped tracksuit and his trainers had come off when she saw him. She stopped her mini to provide protection by preventing other cars from hitting him.
She said she had been told the former Wham! star had tried to adjust his door because it was not properly closed and had fallen out.
Describing his appearance, she told the paper: "There was a nasty cut on his forehead and the back of his head. There was blood all down his face and on his teeth. He was breathing and conscious but in shock."
The singer, who was treated at the scene of last week's motorway accident and then taken to hospital by air ambulance, was close to death only 18 months ago after being struck down with pneumonia in Vienna, but he fought back to perform again.
In 2010 the singer, whose hits include Faith and Freedom, received an eight-week prison sentence following an incident the previous July in which he crashed his Range Rover into a shop in north London. He was also given a five-year driving ban after he pleaded guilty to driving under the influence of drugs and possessing cannabis.
And he had earlier been banned from driving for two years and sentenced to 100 hours of community service in 2006 when he was convicted of driving while unfit through drugs after he was found collapsed in his Mercedes.
A spokeswoman for the singer insisted that he was "fine" although he continued to be kept in hospital for observation, saying: "He's still in hospital but this is standard practice to keep an eye on him. He has a couple of bumps and grazes and cuts to the head, but he's making good progress and looking forward to getting out."