Shanghai - Pressure was mounting on Sunday on the European Tour to investigate caddie Steve Williams after his racial insult aimed at golf legend Tiger Woods caused worldwide revulsion.
Williams sparked outrage when he called his former employer Woods a "black arsehole" after he collected an award during a caddies' gala dinner at the WGC-HSBC Champions in China on Friday evening.
Several leading players - including Williams's new Australian boss Adam Scott - dismissed his racial slur as nothing more than a misguided joke "that should never have left the room".
Williams posted an online statement on Saturday apologising to Woods and admitting his comments "could be construed as racist" after fellow caddies, fans and sponsors reacted with disgust to his remarks.
But the players' casual reaction and silence from the sport's leading officials has been seen as a closing of ranks, and anti-racist groups lined up to condemn the European and PGA tours for failing to censure Williams.
Sally Dhalu, secretary of the UK anti-racism group One Society, Many Cultures, said: "I don't think an apology is enough. The only way to root [racism] out and prevent other people from behaving in the same way is to take disciplinary action.
"An investigation should be conducted," she was quoted as saying by the UK's Daily Telegraph newspaper.
The European Tour has so far refused to comment on the scandal.
But HSBC bank, the main sponsor of Asia's flagship golfing tournament, has been keen to distance itself from the row, which has overshadowed the event in Shanghai.
"Any kind of racially motivated comment in this day and age is unacceptable and cannot be tolerated," HSBC group head of sponsorship Giles Morgan told AFP on Sunday.
"It is not up to us to take action [against Williams] and I understand European Tour officials will be making a statement later today. We are keen to get back to focusing on what is a great golfing tournament," he added.
New Zealander Williams was employed by Woods for 12 years, the pair winning 72 tournaments together with the caddy earning an estimated US$3 million, before their acrimonious split in the summer.
The 47-year-old caddy, who kept silent during Woods's sex scandal, is believed to have struggled to come to terms with his axing and issued a series of barbed comments before his racial slur.
Williams has previously courted controversy with his outspokenness and gruff personality, once calling Phil Mickelson a "right prick", insulting spectators and bullying the media.
He was again due on the first tee with world No 8 Scott on Sunday.
Many golf commentators have expressed surprise that Williams was still carrying the bag of Scott, a rising young star who is keen to foster a supporter-friendly image.
Some golf fans who spoke with AFP Saturday said Williams's apology was insufficient and further disciplinary action should be taken against him for bringing shame on the sport.