According to Dimitri Seluk, who represents the Ivory Coast international, Toure was dismayed that, despite the club giving him a 31st birthday cake, the owners did not personally congratulate him at a post-season party in Abu Dhabi.
Former Barcelona powerhouse Toure, whose goals were instrumental in City’s second title in three seasons, could even leave the club, Seluk said.
“He got a cake but when it was Roberto Carlos’s birthday, the president of (Russian side) Anzhi (Makhachkala) gave him a Bugatti,” Seluk told BBC Sport.
“I don’t expect City to present Yaya with a Bugatti, we only asked that they shook his hand and said ‘we congratulate you’. It is the minimum they must do when it is his birthday and the squad is all together.
“Of course Yaya is upset about this. It is his birthday and nobody said anything or shook his hand, so he does not feel comfortable,” added Seluk, who said City sent a Twitter message wishing Toure a happy birthday.
Toure, who joined City in 2010 as part of the owner Sheikh Mansour’s vast outlay on world-class players, signed a new four-year contract last year and Seluk denied that he was looking for a better deal with the club.
“No. Money is not important. He has enough money,” he said.
“The most important thing is a human relationship and maybe this is his opportunity for Yaya to find that. If City don’t respect him, then easy – Yaya will leave. No problem. It is more important he plays for a club that respects him more than having a few thousand pounds added to his salary.
“I have spoken to him about leaving and we will see what happens but, at the moment, Yaya is really upset.”