Donnarumma's contract is up for renewal in 2018, with the club trying to convince the 18-year-old to sign a new deal.

However, Raiola is delaying entering into negotiations, saying he is working in his client's best interests.

But members of Milan's Curva Sud fan base have accused him of trying to "insert clauses which work in his own favour" in any new deal.

"We are writing these words, unfortunately, because we feel that the situation which has arisen is crazy," a statement published on curvasudmilano.it read.

"We are talking about a phenomenal player, but one who is still very young and is in the hands of a conscienceless agent.

"It's incredible that one person can keep in check a club like Milan and also an 18-year-old who goes from kissing his shirt each Sunday to being the subject of discussion.

"The player's own wishes should be taken into consideration, and also the club's wishes.

"The main aim of this dealer is to find an agreement and insert clauses which work in his own favour, like he did with Juventus and [Paul] Pogba, earning bucketloads of money on a future sale."

Donnarumma is still on youth terms at Milan, earning an estimated €160,000 a year until 2018. A new deal would see him earn up to €5 million a year, although many clubs could offer him better terms.

"A lot is said of Italian football being in a huge crisis, with an economic strength inferior to other nations, but since the rules allow certain people to take money out of the world of football for their own personal gain it is impossible to hope for any growth," the statement added.

"There are clubs abroad who refuse to work with certain agents, but unfortunately at Milan somebody thinks it's a good idea to open the door to certain people."

The statement urged the club management to "free themselves from these people and start afresh with virtues, without being held to ransom by anybody."

And it called on Donnarumma "to show once again his character and love for Milan, but to do so with some real actions."

Milan are keen to resolve the goalkeeper's future before he joins the Italy under-21 squad for the European Championship in Poland next week.