Gareth Thomas has failed in a bid to delay the disciplinary hearing which threatens to wreck the start of his RBS 6 Nations championship.
The former Wales captain faces a misconduct charge after being accused of 'aggressive' and 'offensive' behaviour towards supporters during Toulouse's controversial European Cup game with Ulster on January 21.
The European Rugby Cup disciplinary hearing is set for Thursday in Dublin, three days before Wales open their Six Nations campaign at home to Ireland.
Thomas' lawyers requested a delay to the hearing on legal grounds but their approach was rejected by ERC.
A Welsh Rugby Union statement confirmed: 'Lawyers representing Gareth Thomas have formally asked the ERC to adjourn the disciplinary hearing scheduled for Thursday, but this request has currently been refused.
'Gareth Thomas is still fully involved in the Wales rugby squad preparations for the Six Nations international against Ireland in Cardiff on Sunday.
'The Welsh Rugby Union remains anxious to ensure that Gareth Thomas is treated fairly.'
If found guilty Thomas could receive a suspension that would rule him out of the Ireland game, if not longer.
Even if Thomas is found not guilty, or escapes a suspension, the timing of the hearing will not have helped Wales' preparations.
Gareth Jenkins has already had to delay his team announcement from Monday to Thursday as he waits on Thomas' availability and the fitness of key players like Mark Jones and Shane Williams.
But the coach did receive some positive news today. Jones and Thomas have made 'significant recoveries' from their respective ankle and shoulder injuries and were officially added to Wales' Six Nations squad.
Jones remains doubtful for the Ireland game while Williams, who has a hip injury, is still considered to be in a 'race against time'.
Jenkins added: 'Mark and Jonathan both missed out initially because of the recent problems they have had with injury and they make a welcome return to the national set-up.'
Wales have invited Under-21 wingers Aled Brew and Jamie Roberts to join the training squad in an unofficial capacity.