"I see this [referendum] as something that is beyond abdication of reason; this is critically political inexperience, there cannot be such an understanding of politics," he said in a joint interview broadcast live on three Turkish news channels.
Erdogan stressed that Turkey would not allow steps which would threaten Iraq's territorial integrity.
Iraqi Kurdish Regional Government (KRG) leader Massoud “Barzani knows very well what we think about the issue. His remarks, in my opinion, are very wrong. He knows our stance on Iraq's territorial integrity."
Erdogan said his country would make his stance on the issue even clearer after a national security meeting on Sept. 22, just days before the planned referendum.
PM Yildirim speaks with Iraqi counterpart
Separately, Turkish Prime Minister Binali Yildirim and his Iraqi counterpart Haider Abadi spoke on the phone Friday, and discussed the planned referendum, prime ministry sources said.
According to the sources, who asked not to be named due to restrictions on talking to the media, Yildirim called the Iraqi Kurdish region’s decision to hold an independence referendum a “false step”.
The two leaders agreed to work together to prevent the move.
The Turkish premier also expressed his condolences over Thursday's twin Daesh-led terror attacks that killed over 80 people in Iraq’s southern province of Thi Qar, adding that Ankara will continue to support Baghdad’s fight against terror.
The non-binding referendum will see residents of northern Iraq’s Kurdish region vote on whether or not to declare formal independence from Baghdad.
Baghdad rejects the planned poll, saying it will adversely affect the fight against the Daesh terrorist group, which still maintains a significant presence in northern Iraq.
The Iraqi government also believes that holding the poll would violate the terms of the country's constitution.
Turkey, too, rejects the planned referendum, saying the region’s stability depends on Iraq’s continued unity and territorial integrity.