US broadcaster ESPN was plunged into a race row after one of its commentators compared tennis player Venus Williams to a "gorilla", prompting a flood of criticism online.

Commentator Doug Adler made the remark during the American's match against Stefanie Voegele at the Australian Open on Wednesday, when she won 6-3, 6-2 to reach the third round. 

"She misses a first serve and Venus is all over her," said Adler, a 58-year-old former player. "You see Venus move in and put the gorilla effect on. Charging."

Viewers were quick to register their distaste on social media, while tennis journalist Ben Rothenberg called it "appalling stuff".

"Horrifying that the Williams sisters remained subjected to it still in 2017," he tweeted.

There was no immediate comment from ESPN. 

Venus Williams and her sister Serena, who have 29 Grand Slam titles between them, have experienced negative comments in the past.

In 2014, Russian Tennis Federation President Shamil Tarpischev was forced to apologise after he taunted them as the "Williams brothers".

Source: AFP