Furious tennis fans have called for an American commentator to be fired after he was accused of comparing African-American tennis superstar Venus Williams to a gorilla at the Australian Open.

The controversial comment was made by ESPN's Doug Adler during Williams' second-round match at the first Slam of the year in Melbourne against Stefanie Voegele.

The 59-year-old former professional player was describing the pressure Williams was putting on the second serve of her Swiss opponent.

Venus Williams (pictured) of the U.S. was playing in the second round of the Australian Open when the remark was made

'She misses a first serve and Venus is all over her,' Adler said.

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

What it provoked was a wave of outrage on social media, including from New York Times tennis writer Ben Rothenberg who was furious at the comment.

'This is some appalling stuff,' Rothenberg tweeted.

ESPN's Doug Adler (left) accused of racism after saying Venus Williams (right) had 'put the gorilla effect' on her opponent

Adler's comment sparked outrage on social media with many people showing their anger at what he said

Williams (left) was playing against Switzerland's Stefanie Voegele (right) at Melbourne Park

'Horrifying that the Williams sisters remained subjected to it still in 2017.'

Williams (pictured) won the match

But Rothenberg was not alone in feeling horror at the remark with Richard Ings tweeting: 'That is unacceptable commentary. Appalling stuff.'

Victoria Chiesa tweeted that it wasn't the first time that Adler had overstepped the mark but this was a new low.

'Doug Adler's said some awful things in the commentary booth before, but this is next-level disgusting,' Chiesa wrote.

The criticism rained in from all quarters after this with Shanna just one of many who found his comments 'disgusting'.

'Doug Adler is the commentator that said this. Disgusting beyond words,' Shanna tweeted.

'Or to any person of color it's derogatory and racist. I'm disgusted by ESPN and Doug Adler. Venus is all class and a wonderful role model.'