TELECOMMUNICATIONS giant Optus has become embroiled in a racism row after a store on Sydney's affluent lower north shore advertised for "Anglo Saxon" retail assistants.

An ad posted on Seek on Thursday stated the Neutral Bay outlet was looking for a casual retail consultant and noted it would prefer "candidates who are Anglo Saxon".

The ad, taken down on Friday morning, has been widely condemned by unions, politicians and social media users.

"Optus proudly supports diversity and employs staff representing more than 70 nationalities," Optus human resources vice president Vaughan Paul said in a statement on Friday.

"This error is completely unacceptable and a clear breach of our advertising standards and commitment to equal opportunity employment."

Mr Paul said Optus would be looking to take "disciplinary action" against those involved.

The union representing Optus workers slammed the "blatantly racist" ad and called for an investigation into the company's hiring policies.

"How did this racist requirement end up in an ad at all?" CEPU national secretary Greg Rayner said in a statement.

"This is extremely concerning and we have to get to the bottom of how this happened."

State Greens MP Mehreen Faruqi posted the ad on Facebook noting "Optus Neutral Bay prefers Anglo Saxon applicants".