Cardiff City have been placed under a transfer embargo the Football League for breaching its financial fair play (FFP) regulation - scotching hopes of signing striker Tony Watt on a permanent deal.
The club says it is "extremely disappointed" in the Football League's decision, which bans them from buying players for the remainder of the transfer window, and is adamant it complied with FFP requirements for last season.
In a statement it said: "Having fully disclosed all matters in respect of our FFP position for 2014/15 and having taken independent expert advice, it is our firmly-held view that Cardiff City Football Club has indeed complied with the FFP requirements for season 2014/15 - contrary to the League’s position."
The Bluebirds will now seek further advice before deciding whether or not to appeal the ban.
Charlton striker Watt was expected to make his loan at the Cardiff City Stadium permanent this month, but will now head back to London to link up with the Addicks.
According to the South London Press, Charlton had hoped to raise up to £2m from the sale.
Cardiff are the fourth Championship club to be hit with FFP sanctions from the Football League this season, following Fulham, Nottingham Forest and Bolton who are all currently blocked from buying new players.
Meanwhile, Premier League Bournemouth could face a fine of up to £10m for breaking FFP rules during their promotion-winning campaign last season.
The Football League's FFP rules restricted Championship clubs to a maximum permitted loss of £6m last season.