Manchester City have branded Arsenal manager Arsene Wenger's outspoken comments about UEFA's Financial Fair Play rules "unfounded and regrettable".
Wenger believes there are major questions for City to answer over their record £300million sponsorship deal with Etihad Airlines.
Although the contract includes naming rights for Eastlands, plus a major input into a yet-to-be-built training facility close to the stadium, in addition to an extension of their shirt sponsorship, it is still not entirely clear how City ended up with such a gargantuan sum.
As Etihad are the national airline of Abu Dhabi, home of Blues owner Sheikh Mansour, there are some who feel the figures have been artificially inflated to help City achieved UEFA's demand to live within their means.
Wenger is one, putting City onto the defensive.
"The financial details of the comprehensive agreement announced last week between Manchester City and Etihad Airways remain confidential and figures being speculated about are not accurate," said a club spokesman.
"Manchester City is a pro-active member of the European Clubs Association and is working actively and with transparency with regard to Financial Fair Play.
"In light of these facts, recent comments about the partnership by some observers are unfounded and regrettable."
This might not cut much ice with Wenger who, speaking on Arsenal's Far East tour, had questioned the validity of Financial Fair Play if City could be allowed to negotiate such contracts.
"It raises the real question about the credibility of the financial fair play," said the Gunners boss.
"They give us the message that they can get around it by doing what they want. The difficulty and the credibility of the financial fair play is at stake.
"If financial fair play is to have a chance, the sponsorship has to be at the market price. It cannot be doubled, tripled or quadrupled. If they bring the rules in they have to be respected.
"He [UEFA president Michel Platini] is very strongly determined on that. He is not stupid, he knows that some clubs will try to get around that.
"At the moment I believe they are studying, behind closed doors, how they can really strongly check it.
"That is his big test."