He has since said the word he used was "guerrilla".

During Williams’ second-round match on Wednesday the 59-year-old former player said:

"She (Voegele) misses a first serve and Venus is all over her.

"You see Venus move in and put the gorilla effect on. Charging."

Viewers immediately slammed the commentator on social media.

"Horrifying that the Williams sisters remained subjected to it still in 2017," tennis journalist Ben Rothenberg tweeted.

A report on the ESPN website said: "Because the words gorilla and guerrilla are pronounced similarly, it's impossible to say for certain which word Adler spoke.

"During an Australian Open stream on ESPN3, Doug Adler should have been more careful in his word selection."