Manchester City are fearful of having their ambitious transfer plans jeopardised by unauthorised third parties trying to broker deals on their behalf as the Barclays Premier League club wrestle for the first time with some of the pitfalls of their newfound wealth.

It emerged yesterday that an Arab purporting to be an intermediary of Sheikh Mansour, City’s billionaire owner, had approached the agent of Iker Casillas twice in the past three months indicating that the club were prepared to shatter the world transfer record with a €150million (about £128million) offer to sign the Real Madrid goalkeeper.

While it is not uncommon for agents to attempt to muscle in on deals or for others to be brought on board in an effort to drive through a particular transfer, the behaviour of some individuals is becoming such a worry that Garry Cook, the City executive chairman, felt compelled to issue a statement yesterday denouncing such activity. City are concerned that genuine deals could be affected or prices inflated if such events persist.

“Manchester City has a clear strategy for the future — we want the right players who will take this club forward and through discussions and meetings between myself, Mark Hughes and his technical staff, we have identified a list of targets,” Cook said. “We will be working to bring those players to the club ourselves and we have not given another party or individual a mandate to negotiate on our behalf.

“In spite of recent reports, we are not using intermediaries to negotiate with players. In fact, only last week we refused two agents permission to seek out players on our behalf. Mark Hughes and I very recently met with the chairman, Khaldoon al-Mubarak, to discuss this matter and we are all in agreement — that the mandate for seeking out and securing new playing personnel for Manchester City is ours and ours alone.

“Furthermore, we would also like to assure everyone concerned that we are committed to recruiting only those players who we consider to be the very best and most suitable for Manchester City in the future.”

Although Casillas was always a non-starter, City are working hard to bring Gianluigi Buffon, the Juventus goalkeeper, to the club among a host of other names. While Cook emphasised yesterday that a list of targets had been drawn up, however, it is thought that some of Sheikh Mansour’s associates might be trying to bring in players not necessarily chosen or recommended by Hughes.

Publicly, City deny this and it seems unlikely that the matter would come to a head, although Hughes will endeavour to ensure that all transfer activity is done on his terms. What is not in dispute, though, is that Sheikh Mansour is eager for a complete overhaul of a squad that has struggled at times in the league this season and which, for the moment at least, is not nearly strong enough to compete for the title, the owner’s long-term aim.

As few as six present first-team players could be left around this time next year. Hughes is eager to sign five or six players when the transfer window opens in four weeks’ time, while there is likely to be a flurry of activity next summer. Sven-Göran Eriksson signed eight players at a cost of close to £50 million in the summer of 2007.

Meanwhile, City have been warned about the behaviour of their ballboys after Cristiano Ronaldo, the Manchester United forward, had the ball hurled at him during the derby match on Sunday. The incident happened late in the first half at the City of Manchester Stadium as Ronaldo, who was later sent off for a second bookable offence, was about to take a corner during United’s 1-0 win and was followed by a round of applause.

It resulted in Howard Webb, the referee, instructing Lee Mason, the fourth official, to speak at half-time to City officials, who have reminded the ballboys of their responsibilities.