Wallaby star Tim Horan will have to wait until at least the end of January before making his Heineken Cup debut for Saracens.

An administrative oversight by the north London club means that Horan, whose long-rumoured move to London was first announced back in May, is ineligible for the entire six-match pool stage of the European competition.

European Rugby Cup Ltd (ERC), the organising body of the Heineken Cup, were notified before the registration deadline of 26 September that Horan was one of Saracens' 30 permitted players for the pool matches.

But the final decision on eligibility in competitions rests with the individual Unions in which the clubs are based - in Saracens' case, the Rugby Football Union in England. The RFU told ERC that they had not received the necessary paperwork from Saracens to register Horan in England, and that he was therefore ineligible for the tournament.

Horan missed Saracens' Heineken Cup opener in Toulouse last Saturday, because he is still recovering from an ankle injury. Had he played, Saracens might now be facing a fine or loss of the two points they gained in winning 32-22. Tournament rules allow for two more players to be regeistered for the knockout phase, which begins on the weekend of 27 January.

Saracens owner Nigel Wray has admitted the club's error, but is calling on the administrators to make an exception for one of the game's star names. "Are we saying that for the sake of a piece of paper we want to deprive the public and the tournament of one of the world's best players?" said Wray. "That doesn't make sense, surely. It's bureaucracy gone mad."

That argument is likely to fall on deaf ears at ERC, who have indicated that Saracens were aware of the rules, and cannot be allowed an exception based on their estimation of Horan's worth. The club's only hope is that the RFU will back-track on their initial decision.

Saracens, in common with all the clubs competing in the Heineken Cup, have signed the participation agreement with the organisers which sets out all the commercial and playing rules and regulations for all parties.

Although Horan is unlikely to be fit for Saracens' first four pool matches, he would have expected to have been ready for the last two, at home to Toulouse and away to Ulster in mid-January, which could be crucial in determining qualification for the lucrative knockout stages.

Overall responsibility for any mix-up will probably rest with the club's chief executive, Francois Pienaar.

French champions Stade Français were fined £5000 for fielding Samoan wing Brian Lima against Leinster in last season's Heineken Cup, when the player had not been properly registered.

Leinster, despite winning the match in question, objected to the ERC ruling. This was rejected by ERC and Stade Français were allowed to continue to the quarter-finals, while Leinster were eliminated.

ERC will be anxious to be seen to be upholding the rules this time round, because there were suggestions in the Lima case that they were aware of his ineligibility before he played in the Leinster match.