World number two Caroline Wozniacki claims her parents were subjected to death threats as she lost in the Miami Open to Puerto Rico's Monica Puig.
Wozniacki, who won her maiden Grand Slam at the Australian Open, said she and other family members - including children - were also verbally abused.
"When certain lines are crossed it makes tennis miserable for both competitors," she said.
The Dane, 27, also accused security staff of "accepting" the alleged abuse.
Wozniacki eased through the opening set before going on to lose 0-6 6-4 6-4 to Puig, who is the reigning Olympic champion and ranked 82nd in the world.