"Member States should prioritise the immediate transfer of people from overcrowded sites on the islands to open facilities on the mainland that meet European law standards for reception, rather than pressuring Greek authorities to keep people on islands in substandard conditions," the statement said.
"European countries are shifting their protection responsibilities on to countries outside the EU, even at the cost of violating European and international law. They have failed to come together and collectively manage the new arrivals of people, instead putting huge pressure on just a few countries to manage the process and consequences of Europe-wide policies," the statement said.
At the December 15 European Council meeting, the EU leaders have the opportunity to ensure that people arriving in Europe will be treated humanely, responsibly and that their rights will be safeguarded, the watchdogs added.
Currently returns under the Dublin rules are temporarily put on hold after the European Court of Human Rights ruled in 2011 that due to degrading treatment of migrant the Greek asylum centers were not save to return asylum seekers there. The European Court of Justice has also ruled against transfers.