"This is a disgrace for those [EU] member states which are not willing to accept refugees and are leaving Greece alone [to deal] with this problem," Schulz told the German newspaper Neue Osnabrucker Zeitung.
EU countries that have refused to accept refugees are the ones to blame for this state of affairs, he added.
Until recently, the camp in Idomeni was hosting some 8,400 refugees and migrants, including many families with children, who for the most part had fled war and persecution in the Middle East. Following decisions by many Balkan states to close their borders with Greece the camp grew in size to about 14,000 migrants.
The process of transferring refugees from the camp in Idomeni to other locations began on Tuesday. More than 700 police officers are supervising the process.