New Zealander Williams called Woods a "black arsehole" during the annual caddies' awards at the HSBC Champions inShanghai.

He made the extraordinary outburst when asked about his controversial celebrations following a victory by his new employer, Australian Adam Scott, at the Bridgestone Invitational in August.

Williams, who was sacked by Woods in July after being at the former world No 1's side for 13 of his 14 major championship titles, described Scott's victory as the "best win of my career".

Addressing the room after being handed a tongue-in cheek "celebration of the year" gong, Williams, 47, shocked players, fellow caddies and sponsors by saying: "It was my aim to shove it right up that black arsehole."

Williams later issued an apology on his kiwicaddy.co.nz website.

"I apologise for comments I made last night," he said in the statement.

"I now realise how my comments could be construed as racist. However I assure you that was not my intent. I sincerely apologise to Tiger and anyone else I have offended."

Nevertheless there were calls in the British media for Williams to be sacked by world number eight Scott and thrown out of the game.

Scott was among a clutch of top 10 players including Rory McIlroy among the 100-strong audience listening to Williams' comments in the banqueting hall.

Scott, 31, teed off on Saturday with Williams at his side as the storm around his caddy's comments gathered strength, and moved up to joint first with Swede Freddie Jacobson on 12 under during the first nine of the third round.

Officials at the WGC-HSBC Champions, Asia's flagship event sanctioned by the PGA and European tours, were said to be embarrassed by Williams' slur but were keeping silent on the scandal.