He was charged with misconduct by the Football Association yesterday after failing a random test at Ipswich's training ground on 9 December. He has 14 days to respond.
Because cocaine is considered a performance-enhancing drug, the FA has a tougher range of punishments they could impose on Tanner.
"We are in constant touch with the FA over drug issues and the first step we always try to take is to do all we can to help rehabilitate the player concerned," said Gordon Taylor, the chief executive of the Professional Footballers' Association. "It is only when the player is unwilling to help himself that punitive action is considered and taken against first- time offenders.
"But although there is a desire to help players, it must also be realised that there is a grading of penalties and these increase when the drug in question is performance-enhancing rather than purely social."
The last high-profile cocaine user, Orient's Roger Stanislaus, banned by the FA for a year last season and then sacked by the London club.
The Charlton teenager Jay Notley is the only other player known to have tested positive this season out of over 300 samples, the FA doping control unit exposing a cocktail of cocaine, Ecstasy and cannabis.
He has so far been treated leniently because of his age, the FA sending him to a rehabilitation centre for assessment, and he is due to face a further hearing in March. Tanner cannot expect such leniency, given his experience and profile, although Ipswich have promised to stand by him throughout the ordeal.
The Ipswich chairman, David Sheepshanks, only yesterday elected as chairman of the Football League, said: "We deplore the use of drugs and Ipswich Town would like to emphasise that we are fully supportive of the stance being adopted by the FA to eradicate it from the sport.
"The player is aware of the damage done both to his reputation and to that of the club and has expressed his apology and great regret. He has been disciplined by us but now, however, the matter is out of our hands and will be dealt with the FA."Reuse content