Western Sydney Wanderers apologise to Arnold over banner

The Western Sydney Wanderers have issued a formal apology to Sydney FC coach Graham Arnold over the offensive banner which marred last weekend's Sydney derby at ANZ Stadium.

The Wanderers on Thursday were fined $20,000 over the sign held aloft by members of the Red and Black Bloc, depicting Arnold engaging in a sex act.

The club also banned 14 RBB members, and threatened to shut down its entire area indefinitely.

The Wanderers have apologised to Sydney FC coach Graham Arnold. (AAP)

On Saturday - a week after the incident - the Wanderers released a statement of apology.

"Unfortunately the events of the last week have overshadowed what we should be celebrating as a fantastic event between Sydney's two A-League teams," said Wanderers chairman Paul Lederer.

"It is with great disappointment that the actions of a minority have prompted fairly stern action to be taken by the club this week to eradicate anti-social behaviour.

"On behalf of the Western Sydney Wanderers, we apologise to Graham Arnold and his family and to all others who have been offended by the abhorrent actions of a few who are now no longer part of our club."

But the apology appears to have fallen on deaf ears, with Arnold saying on Wednesday that the Wanderers had left it too late to make it up to him.

"I would probably have liked one (an apology) by now," Arnold said.

"I haven't heard from them ... so I don't want one now."