A group of jockeys started brawling at a barbecue after a woman took her top off and hugged one of the riders.
During the fight at Cambridge, a woman guest received two black eyes after being hit by a stray punch.
Australian-born jockey Pat Ferris, 29, who rode
two winners in Tauranga and Te Awamutu, attended the barbecue on Sunday with his girlfriend Jenna Bartram.
A row started when a woman took off her top and began hugging him. "A couple of guys were not too happy with that," he said.
"Everyone had a little too much to drink. People were getting rowdy and a scuffle broke out.
"About five or six people were involved and my girlfriend got hurt, there was a little bit of blood coming from her nose. I don't know what happened so I gave her a hug and took her away."
The couple became separated when the scuffle resumed.
Ferris drove off from the party to look for his girlfriend, a Cambridge strapper.
But he was stopped by a plain clothes police officer and tested for drink-driving. Ferris said he refused to give a blood specimen and was aware he would now probably lose his driving licence.
He said Ms Bartram had got caught in the crossfire.
Ferris took exception to the way police treated him. He said he was handcuffed, taken to the Hamilton Police Station and strip searched.
He was released after four hours in police cells and only got his clothes back yesterday.
Sergeant Gordon Grantham, of Cambridge police, confirmed a man had been charged with refusing to give a blood sample.
He said an "initial report" regarding an alleged assault had been received and police were waiting for the victim to come forward.
Ms Bartram said she would not lay a complaint and did not know who struck her. "There were arms and legs flying everywhere."
She was trying to break up the fight because she didn't want anyone getting hurt, "but I was the one who ended up getting hurt".
Racecourse inspector Bryan McKenzie said racing authorities did not intend taking action at this stage.
