Theo De Vries was enjoying a getaway with the Girls Aloud singer on New Year’s Eve in Austria, when the argument erupted.
He alleges Harding (pictured) “bit” him on the leg, flung an ashtray at his head and left him with a bloody nose after hitting him in the face.
He said: “I have a big black eye. Sarah bit me on my leg. I went to the hospital to get an injection. It’s very dangerous, I have a big scar on my leg now with five teeth marks.
“She threw an ashtray at my head, hitting my eye. She gave me a bloody nose. Don’t forget that she is a very good kick-boxer. She has done a lot of kick-boxing in the past.”
Despite the 30-year-old star – who left an American rehabilitation facility in October after being treated for alcoholism and depression – being spotted arriving back in the UK with a bandaged arm, De Vries has rubbished claims he was the aggressor in the argument.
He added in an interview with The Sun newspaper: “It’s zero per cent the truth. I want everyone to know that I am a normal decent man. I didn’t hit Sarah one time.
“I really had to laugh at that picture. Sarah is an actress and don’t forget it.”
However, insiders have suggested Sarah was acting in “self-defence” and plans to press charges against De Vries, who she had reportedly been dating for three months.
A source said: “Sarah is still really shaken up. She has decided to press charges once she has had time to recover. She was acting in self defence. She bit Theo because she was on the ground and it was her last line of defence.
“She had deliberately flown to Austria to avoid the temptation of drinking. Theo turned up and hit the bottle when she told him their relationship was over.”
Meanwhile, Austrian police have suggested Sarah – who called off her engagement to former fiance Tom Crane in September – is not under suspicion following the incident.
A spokesperson explained: “Officers were called to calm things down after a relationship-related incident.
“A woman filed a complaint against a man from the Netherlands. He was questioned and then released. A report is being prepared for prosecutors who will decide if assault charges are filed.”