Cardiff insist the signing of Craig Bellamy "adds up in a business and sports context" after it emerged the Football League wanted information from the club regarding the deal before registering the player.
League chairman Greg Clarke wants the loan deal for the Wales captain to be closely scrutinised because the npower Championship club have debts estimated at £30million and are being threatened with a winding-up order by Scottish side Motherwell over an unpaid transfer fee.
Clarke said yesterday: "We have to register the player and we've asked Cardiff for some information, which will be confidential between them and us, which will allow us to appraise whether we are going to register that player or not.
"I wouldn't approve of any club taking on more obligations if they couldn't pay their existing ones."
The Bluebirds expressed disappointment at Clarke airing his concerns over the deal in public and intend to contact the League this morning to discuss the matter.
A club statement read: "We are fully confident that this deal adds up in a business and sports context.
"It should be remembered that the club has released 10 players this summer, and to date have brought in two free agents and season-long loan players.
"We are extremely proud to have reached a sensible deal with Manchester City which has allowed us to bring Craig home to realise his dream of playing for his home town club and to help us pursue our ambition of challenging to join the Premier League.
"This deal has also been fully supported and underwritten by our Malaysian investors who have shown unprecedented support since joining the club.
"By bringing Craig Bellamy to Cardiff City we continue to work in the interests of the club, the city and Wales. We will be in contact with the Football League on Thursday morning to discuss these matters further."
Clarke also raised concerns regarding the increase of payments to agents throughout the League after it was revealed Championship clubs paid out a combined total of £10,131,314 during the period from July 1 2009 to June 30 2010.
Spending on agents' fees increased by £3.9million across the whole of the Football League last year.
The Bluebirds' fees were relatively low at £313,000, while Middlesbrough were the biggest spenders, splashing out £1,464,200.
Clarke added: "Given the current economic climate, it is worrying to see such a significant amount leaking from the game.
"This year's figures demonstrate a considerable increase on those of last season and it is essential that clubs work to reduce this liability over the coming campaign."