Ben Tune has been ordered to appear before a disciplinary tribunal by the Australian Rugby Union 16 months after it failed to reveal that the Wallaby wing had tested positive for a banned drug.

The ARU has been under pressure since admitting earlier this week that Tune had unknowingly been prescribed a banned drug and that officials had decided to keep the matter secret. Strath Gordon, a spokesman for the ARU, promised yesterday: "Our tribunal will be 100% transparent and squeaky clean."

Tune was prescribed probenecid, a banned substance under International Rugby Board rules, in March last year to help cure a knee injury. He was withdrawn from four Super 12 matches until traces of the drug had left his body.

The ARU has been asked to provide a chronology of events to the IRB and conceded that it should have told the game's governing body of Tune's predicament at the time. If Tune is found guilty of a dop ing offence at next month's hearing he faces a mandatory two-year suspension under IRB rules.

Tune had played two Super 12 matches for the Queensland Reds - against Canterbury Crusaders and ACT Brumbies - before it was realised that probenecid, which can be used as a masking agent for other drugs, was on the IRB's banned list.

The ARU has decided not to withdraw Tune from today's Tri-nations Test against South Africa in Brisbane after taking legal advice.

"Our lawyer is quite clear. In these unusual circumstances, and having read the regulations, we are not required to stand him down although South Africa's rugby union lawyer might interpret them in another way," said Gordon.

South Africa's manager Gideon Sam said that he was satisfied the ARU would handle the matter correctly. "We have enough confidence in their integrity and that they will do justice to the whole case," he added. "It's for the ARU and the IRB to sort out."