Telecommunications giant Optus has launched an internal investigation after a job advertisement calling for white candidates at one of its Sydney stores was posted online.

The ad for a casual retail consultant appeared on employment portal Seek on Thursday afternoon, and said people "who are Anglo Saxon" would be preferred.

The company has since removed the ad, which was calling for workers at its Neutral Bay store.

ABC News contacted Optus after the ad was circulated on Twitter.

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Optus vice-president of human resources Vaughan Paul said the company had started an internal investigation into how the ad was placed.

He said those involved faced disciplinary action.

"This incident is unacceptable and does not reflect Optus' values of diversity and inclusion," Mr Paul said.

"This error [is] a clear breach of our advertising standards and commitment to equal opportunity employment. Optus proudly supports diversity and employs staff representing more than 70 nationalities."

Twitter user Catherine Snelson who spotted the ad tweeted at Optus and Seek, the website where it was originally posted, writing: "What were they thinking!"

Another, Edward Miller, tweeted at Optus simply saying: "Well, this is not OK"

Optus replied to both Twitter users, stating the offending adv had been removed.

The Optus Neutral Bay store. ( Nick Sas )

The Union representing Optus workers, the Communications Workers Union, called for an independent investigation and a transparent review of the telco's hiring policies.

"It's a racist ad," CWU spokesperson Greg Rayner said.

"It's looking to exclude certain individuals from even applying for a job based on their ethnicity.

"It's unbelievable in this day and age that an ad such as this would even see the light of day. It shouldn't be happening, it's ridiculous."

'They should really have a long hard look at themselves'

ABC News visited the Neutral Bay store on Friday, where staff had no idea about the job ad and had to be shown the ABC's story.

Norman Hussey, a Neutral Bay local, said it was a "very silly move" by Optus. ( Nick Sas )

Staff at the store said the store manager would be back on Monday. They did not know who was responsible for the ad.

Neutral bay local Norman Hussey, 74, said he could not believe a business would advertise something like that in 2018.

"They should really have a long hard look at themselves," he said.

Another local, Astrid Smith, 61, said it was "wrong".

"It's breaking the law isn't it?" she said. "I've been living in the area for 30 years, and yes, it would stop me going in that store."

Tom Carlin, 23, said it was "un-Australian" to discriminate like that.

"We're an inclusive nation, and they should realise that," he said.