Dimitry Seluk claims City have not made Toure feel valued and appreciated,
especially on his 31st birthday last Tuesday which clashed with a party in Abu Dhabi to celebrate City's title triumph.
"Yaya is so upset he's thinking of leaving City," Seluk is quoted as saying by The Sun.
"There are a number of things that have happened that have left Yaya feeling bitterly upset. He must concentrate on the World Cup now.
"But City have treated him with disrespect and have really hurt him."
Toure only signed a new long-term deal last year, but Selcuk says money is not an issue.
"They don't know that money can't buy relationships - no Sheikh can buy a relationship," he said.
"This isn't about money or a new contract - it's about human relationships and City have shown they don't respect him.
"I repeat, this is not about money. In fact, he would take less to return to Barcelona."
Toure is set to link up with the Ivory Coast squad ahead of this summer's World Cup finals.