Former NRL stars Joe Williams and Petero Civoniceva speak out against alleged racist slurs directed at Knights centre Dane Gagai on Sunday.

Dane Gagai has reportedly been the target of racial slurs following Newcastle's heavy defeat to the Sharks at Hunter Stadium on Sunday.

Former NRL player turned boxer and motivational speaker Joe Williams took to social media on Sunday to express his outrage, after being informed of racial jibes directed towards Knights star Dane Gagai yesterday.

Gagai was physically upset following the 62-0 loss to the Sharks, and had to be consoled by teammate Tariq Sims. It was later revealed that Gagai's grandmother had passed away earlier in the day.

It is then that a patron allegedly called him "sooky black c**t", in an abusive outburst which was heard by two friends of Williams. The two were sitting in bay 55 and bay 56 of the Western Grandstand, and say they heard the slurs, but did not see the person responsible.

"It's easy for a fan to think he was upset about the actual game but knowing a little bit deeper there have been some family issues going on and he has lost a close family member, not too long before the game," Joe Williams told NITV News.

"The poor kid's upset and he is upset for a reason, and then we have clowns in the audience that were yelling out racial jibes and abuse towards Dane. That sort of rubbish is just not on mate."

Williams said he has had enough of this type of behaviour and asked that both Indigenous and non-Indigenous people need to stand together when incidents like this arise.

"We need to start looking to our non-Indigenous people in the crowds who hear these things. We have to ask them to be allies for us. At the end of the day what you ignore is what you accept," he says.

"That's a packed stadium yesterday, and if this guy if my friends are hearing it from a fair distance away there has to be people a lot closer that hear these sort of things."

"We need to start looking to our non-Indigenous people in the crowds who hear these things. We have to ask them to be allies for us."

"They haven't said boo. It's always the Aboriginal and Torres Strait Islander people standing up and saying you know what, enough is enough, we are sick of this racism."

Former Australian rugby league player Petero Civoniceva, who responded to Williams tweet last night, said there was no place for racism in our game, telling NITV News that if identified, perpetrators of racism should be banned for life.

"To stoop to that level is the most upsetting thing, in a round where we are celebrating the contribution of Indigenous players and celebrating their culture. I think as a game we need to make a very strong statement," he said.

"If we want to send a really strong message, I am sure there is enough CCTV footage to understand where these guys were sitting, identify them, then as a game we can make it clear so all our supporters understand what is right and what is wrong."

The Newcastle Knights told NITV News it is aware about the social media comment and had informed the NRL Integrity Unit for further investigation.