Dundee United have dismissed claims from a group of influential fans that a figure in excess of £500,000 in commission from transfer fees has been paid to unnamed parties.
The Arabtrust and the Federation of Dundee United Supporters Clubs made the claim in a joint letter.
It expressed their shock that more than 25% of £6.3m in transfer fees had been paid out in commission.
But United dispute the figure and say they have no idea where it came from.
A United spokesman said: "We've been reluctantly drawn into this matter and have no wish to enter a war of words, but the £500,000 figure is an entirely fictitious amount based on an incorrect assumption.
"At no time was that figure provided to anyone, so it's surprising to see it in the public domain."
The two fans groups say the payments relate to the sale of four players - Ryan Gauld to Sporting Lisbon, Andrew Robertson to Hull City and Stuart Armstrong and Gary Mackay-Steven to Celtic.
In the statement, they also took issue with Tannadice chairman Stephen Thompson's quoted level of investment in the club.
"This does not include payments to players, agents or other clubs," they said. "When all of these various payments are totalled, over 25% of the £6.3m in fees received has not been kept in the club."
The statement also expressed worries over club debts, noting that: "Despite the sales of the four players noted above, the board of DUFC does not believe that this is yet sufficient to pay all current remaining debt.
"The amount of investment in the club by the Thompson family is not £5m as has been widely reported.
"This includes payments of over £1m made to buy out previous shareholders and soft loans to the club, the latter of which have been steadily repaid in the last few years.
"The actual investment, as confirmed by Stephen Thompson, is nearer £3.5m. Of this, the Thompson family hold nearly 85,000 shares in the club, which are valued (as agreed by the clubs auditors) at £33 a share.
"We believe that, if the Thompson family were to sell their shares, they could recoup a significant proportion of the money they have invested.
United responded to the claims, telling supporters "at all times the board acts to promote the success of Dundee United".
A statement on the official website said: "All supporters can be assured that the board will continue to implement its professional and comprehensive strategy for the football club.
"This strategy and the related actions of the chairman and board of directors have delivered progress both on and off field.
"Off field, the board has reduced overall debt, including Thompson family loans, from £5.2m in February 2014 to £2.6m while successfully extricating the club from all bank debt," they added.
"The club debt is projected to be reduced to £1.4m by the end of this year. And, in a period where Scottish football clubs have faced some of the most challenging economic times in history, the club continues to pursue its strategic objectives and invests in facilities for the future."
BBC Scotland understands the club is also concerned about an apparent breach of confidentiality, having understood that both the correspondence sent to and replied to by the club were to be held in the strictest confidence.